feat(inventory): add repair resolution workflow and invoice correction logic

- Add repair resolution mechanism (`resolve_repaired_item`) allowing users to:
  * Just repair: Return item to normal state (`Verfuegbar: True`)
  * Replace: Update `Code_4` (inventory/barcode) and restore availability
  * Delete: Remove item and update series counts (`SeriesCount`) and parent/child references
- Support `Code_4` updates in `update_item` for specific physical items
- Implement invoice correction route (`admin_add_invoice_correction`) with audit logging
- Add modal UI in library admin view to handle repair actions and code replacements

Web/app.py

@@ -6743,7 +6743,6 @@ def mark_damage_repaired(id):
         if result.matched_count == 0:
             return jsonify({'success': False, 'message': 'Objekt nicht gefunden.'}), 404
 
-        # Best-effort system log entry for repair action
         try:
             logs_collection = db['system_logs']
             logs_collection.insert_one({
@@ -8840,132 +8839,145 @@ def admin_mark_invoice_paid(borrow_id):
             client.close()
 
 
-@app.route('/admin/borrowings/<borrow_id>/invoice/finalize', methods=['POST'])
-def admin_finalize_invoice_and_repair(borrow_id):
-    """Mark invoice as paid and item as repaired in one action."""
+@app.route('/admin/borrowings/<borrow_id>/invoice/pay', methods=['POST'])
+def admin_mark_invoice_paid(borrow_id):
+    """Mark invoice as paid."""
     if 'username' not in session:
-        flash('Ihnen ist es nicht gestattet auf dieser Internetanwendung, die eben besuchte Adrrese zu nutzen, versuchen sie es erneut nach dem sie sich mit einem berechtigten Nutzer angemeldet haben!', 'error')
+        flash('Ihnen ist es nicht gestattet, versuchen sie es erneut nach Anmeldung!', 'error')
         return redirect(url_for('login'))
 
     current_permissions = us.get_effective_permissions(session['username'])
-    
     if not current_permissions['pages'].get('admin_borrowings', False):
-        flash('Ihnen fehlen die nötigen Berechtigungen, um diese Aktion auszuführen.', 'error')
-        return redirect(url_for('home_admin'))
+        flash('Ihnen fehlen die nötigen Berechtigungen.', 'error')
+        return redirect(request.referrer or url_for('home_admin'))
 
     client = None
     try:
         client = MongoClient(MONGODB_HOST, MONGODB_PORT)
         db = client[MONGODB_DB]
         ausleihungen = db['ausleihungen']
-        items_col = db['items']
 
         borrow_doc = ausleihungen.find_one({'_id': ObjectId(borrow_id)})
         if not borrow_doc:
             flash('Ausleihung nicht gefunden.', 'error')
-            return redirect(url_for('admin_borrowings'))
+            return redirect(request.referrer or url_for('admin_borrowings'))
 
         invoice_data = borrow_doc.get('InvoiceData') or {}
         if not invoice_data:
             flash('Für diese Ausleihung existiert keine Rechnung.', 'warning')
-            return redirect(url_for('admin_borrowings'))
-
-        item_doc = None
-        item_id = borrow_doc.get('Item')
-        if item_id:
-            try:
-                item_doc = items_col.find_one({'_id': ObjectId(item_id)})
-            except Exception:
-                item_doc = items_col.find_one({'_id': item_id})
+            return redirect(request.referrer or url_for('admin_borrowings'))
 
         now = datetime.datetime.now()
+        update_fields = {'LastUpdated': now}
 
-        update_fields = {
-            'LastUpdated': now,
-        }
+        # Rechnung auf bezahlt setzen
         if invoice_data.get('paid') is not True:
             update_fields.update({
                 'InvoiceData.paid': True,
                 'InvoiceData.paid_at': now,
                 'InvoiceData.paid_by': session.get('username', ''),
             })
+
+        # Ausleihe abschließen, falls noch aktiv
         if borrow_doc.get('Status') == 'active':
             update_fields['Status'] = 'completed'
             update_fields['End'] = now
 
         ausleihungen.update_one({'_id': borrow_doc['_id']}, {'$set': update_fields})
 
-        repaired = False
-        resolved_count = 0
-        if item_doc:
-            open_reports = item_doc.get('DamageReports', []) or []
-            resolved_count = len(open_reports)
-            item_update = {
-                '$set': {
-                    'DamageReports': [],
-                    'HasDamage': False,
-                    'Verfuegbar': True,
-                    'LastUpdated': now,
-                },
-                '$unset': {
-                    'User': '',
-                    'Condition': '',
-                },
-            }
-            if open_reports:
-                repair_entry = {
-                    'repaired_by': session['username'],
-                    'repaired_at': now,
-                    'resolved_reports': open_reports,
-                }
-                item_update['$push'] = {'DamageRepairs': {'$each': [repair_entry], '$position': 0}}
-
-            item_result = items_col.update_one({'_id': item_doc['_id']}, item_update)
-            repaired = item_result.matched_count > 0
-
+        # Logging
         try:
-            logs_collection = db['system_logs']
-            logs_collection.insert_one({
-                'type': 'damage_invoice_finalize',
+            db['system_logs'].insert_one({
+                'type': 'invoice_paid',
                 'timestamp': now.isoformat(),
                 'user': session.get('username'),
                 'borrow_id': borrow_id,
-                'item_id': str(item_doc.get('_id')) if item_doc else '',
                 'invoice_number': invoice_data.get('invoice_number', ''),
                 'amount': invoice_data.get('amount'),
-                'repaired': repaired,
-                'resolved_damage_reports': resolved_count,
                 'ip': request.remote_addr,
             })
         except Exception as log_err:
-            app.logger.warning(f"Damage invoice finalize log write failed for borrow {borrow_id}: {log_err}")
+            app.logger.warning(f"Log failed: {log_err}")
 
         _append_audit_event_standalone(
-            event_type='invoice_finalized_and_repaired',
+            event_type='invoice_paid',
             payload={
                 'borrow_id': borrow_id,
-                'item_id': str(item_doc.get('_id')) if item_doc else '',
                 'invoice_number': invoice_data.get('invoice_number', ''),
                 'amount': invoice_data.get('amount'),
-                'repaired': repaired,
-                'resolved_damage_reports': resolved_count,
             }
         )
 
-        if repaired:
-            flash('Rechnung als bezahlt markiert und Element als repariert abgeschlossen.', 'success')
-        else:
-            flash('Rechnung als bezahlt markiert. Element konnte nicht repariert werden (nicht gefunden).', 'warning')
-        return redirect(url_for('admin_borrowings'))
+        flash('Rechnung erfolgreich als bezahlt markiert.', 'success')
+        return redirect(request.referrer or url_for('library_loans_admin'))
     except Exception as e:
-        app.logger.error(f"Error finalizing invoice/repair for borrow {borrow_id}: {e}")
-        flash('Fehler beim Kombinieren von bezahlt und repariert.', 'error')
-        return redirect(url_for('admin_borrowings'))
+        app.logger.error(f"Error marking invoice paid for borrow {borrow_id}: {e}")
+        flash('Fehler beim Markieren als bezahlt.', 'error')
+        return redirect(request.referrer or url_for('library_loans_admin'))
     finally:
         if client:
             client.close()
 
 
+@app.route('/admin/items/<item_id>/repair', methods=['POST'])
+def mark_damage_repaired(item_id):
+    """Mark item as repaired and make it available again."""
+    if 'username' not in session:
+        return redirect(url_for('login'))
+
+    client = None
+    try:
+        client = MongoClient(MONGODB_HOST, MONGODB_PORT)
+        db = client[MONGODB_DB]
+        items_col = db['items']
+
+        try:
+            obj_id = ObjectId(item_id)
+        except Exception:
+            obj_id = item_id
+
+        item_doc = items_col.find_one({'_id': obj_id})
+        if not item_doc:
+            flash('Element nicht gefunden.', 'error')
+            return redirect(request.referrer or url_for('library_loans_admin'))
+
+        now = datetime.datetime.now()
+        open_reports = item_doc.get('DamageReports', []) or []
+
+        item_update = {
+            '$set': {
+                'DamageReports': [],
+                'HasDamage': False,
+                'Verfuegbar': True,
+                'LastUpdated': now,
+            },
+            '$unset': {
+                'User': '',
+                'Condition': '',
+            },
+        }
+
+        # Historie der Reparaturen speichern
+        if open_reports:
+            repair_entry = {
+                'repaired_by': session['username'],
+                'repaired_at': now,
+                'resolved_reports': open_reports,
+            }
+            item_update['$push'] = {'DamageRepairs': {'$each': [repair_entry], '$position': 0}}
+
+        items_col.update_one({'_id': item_doc['_id']}, item_update)
+
+        flash('Element wurde erfolgreich als repariert markiert und ist wieder verfügbar.', 'success')
+        return redirect(request.referrer or url_for('library_loans_admin'))
+    except Exception as e:
+        app.logger.error(f"Error repairing item {item_id}: {e}")
+        flash('Fehler bei der Reparatur.', 'error')
+        return redirect(request.referrer or url_for('library_loans_admin'))
+    finally:
+        if client:
+            client.close()
+
 @app.route('/admin/borrowings/<borrow_id>/invoice/pdf', methods=['GET'])
 def admin_view_invoice_pdf(borrow_id):
     """View a previously created invoice PDF for a borrowing."""
@@ -9026,15 +9038,19 @@ def admin_view_invoice_pdf(borrow_id):
 def admin_add_invoice_correction(borrow_id):
     """Append an invoice correction entry without mutating the original invoice body."""
     if 'username' not in session:
-        flash('Ihnen ist es nicht gestattet auf dieser Internetanwendung, die eben besuchte Adrrese zu nutzen, versuchen sie es erneut nach dem sie sich mit einem berechtigten Nutzer angemeldet haben!', 'error')
+        flash('Bitte melden Sie sich an, um auf diese Seite zuzugreifen.', 'error')
         return redirect(url_for('login'))
 
     current_permissions = us.get_effective_permissions(session['username'])
-            
+
     if not current_permissions['pages'].get('admin_borrowings', False):
         flash('Ihnen fehlen die nötigen Berechtigungen, um diese Aktion auszuführen.', 'error')
         return redirect(url_for('home_admin'))
 
+    if not ObjectId.is_valid(borrow_id):
+        flash('Ungültige Ausleih-ID.', 'error')
+        return redirect(url_for('admin_borrowings'))
+
     client = None
     try:
         client = MongoClient(MONGODB_HOST, MONGODB_PORT)
@@ -9064,6 +9080,7 @@ def admin_add_invoice_correction(borrow_id):
 
         now = datetime.datetime.now()
         correction_number = f"CORR-{now.strftime('%Y%m%d-%H%M%S')}-{str(borrow_doc.get('_id'))[-6:].upper()}"
+
         correction_entry = {
             'correction_number': correction_number,
             'reason': correction_reason,
@@ -9095,6 +9112,7 @@ def admin_add_invoice_correction(borrow_id):
 
         flash('Korrekturbuchung wurde revisionssicher ergänzt.', 'success')
         return redirect(url_for('admin_borrowings'))
+
     except Exception as e:
         app.logger.error(f"Error creating invoice correction for borrow {borrow_id}: {e}")
         flash('Fehler beim Anlegen der Korrekturbuchung.', 'error')
@@ -9104,6 +9122,106 @@ def admin_add_invoice_correction(borrow_id):
             client.close()
 
 
+def resolve_repaired_item(item_id, action, new_code_4="", current_user="admin"):
+    """
+    Verarbeitet Items aus der Reparatur und aktualisiert die Serien-Counts
+    sowie Parent/Child-Abhängigkeiten beim Löschen korrekt.
+    """
+    if not ObjectId.is_valid(item_id):
+        return False, "Ungültige Item-ID."
+
+    try:
+        with MongoClient(cfg.MONGODB_HOST, cfg.MONGODB_PORT) as client:
+            db = client[cfg.MONGODB_DB]
+            items = db['items']
+
+            item = items.find_one({'_id': ObjectId(item_id)})
+            if not item:
+                return False, "Item nicht in der Datenbank gefunden."
+
+            series_group_id = item.get('SeriesGroupId')
+
+            # --- OPTION 1: DELETE ---
+            if action == 'delete':
+                is_parent = not item.get('IsGroupedSubItem')
+
+                if is_parent and series_group_id:
+                    sibling = items.find_one({
+                        'SeriesGroupId': series_group_id,
+                        '_id': {'$ne': ObjectId(item_id)},
+                        'Deleted': {'$ne': True}
+                    })
+
+                    if sibling:
+                        new_parent_id_str = str(sibling['_id'])
+
+                        # 1. Mache das Geschwister-Item zum neuen Parent
+                        items.update_one(
+                            {'_id': sibling['_id']},
+                            {'$set': {
+                                'IsGroupedSubItem': False,
+                                'ParentItemId': None
+                            }}
+                        )
+
+                        # 2. Leite alle anderen verbleibenden Sub-Items auf den neuen Parent um
+                        items.update_many(
+                            {
+                                'SeriesGroupId': series_group_id,
+                                '_id': {'$nin': [ObjectId(item_id), sibling['_id']]}
+                            },
+                            {'$set': {'ParentItemId': new_parent_id_str}}
+                        )
+
+                # Physisch aus der Datenbank löschen (Hard Delete)
+                items.delete_one({'_id': ObjectId(item_id)})
+
+                # ALTERNATIVE (Soft Delete have to see if it makes sense):
+                # now = datetime.datetime.now()
+                # items.update_one(
+                #     {'_id': ObjectId(item_id)},
+                #     {'$set': {'Deleted': True, 'DeletedAt': now, 'DeletedBy': current_user}}
+                # )
+
+                # SeriesCount bei ALLEN verbleibenden Items dieser Serie um 1 reduzieren
+                if series_group_id:
+                    items.update_many(
+                        {'SeriesGroupId': series_group_id},
+                        {'$inc': {'SeriesCount': -1}}
+                    )
+
+                return True, "Item wurde gelöscht und der Bestand aller Serien-Items angepasst."
+
+            # --- OPTION 2: REPLACE ---
+            elif action == 'replace':
+                items.update_one(
+                    {'_id': ObjectId(item_id)},
+                    {'$set': {
+                        'Code_4': str(new_code_4).strip(),
+                        'Verfuegbar': True,
+                        'LastUpdated': datetime.datetime.now()
+                    }}
+                )
+                return True, f"Item wurde ersetzt. Neuer Code 4 zugewiesen: {new_code_4}."
+
+            # --- OPTION 3: JUST REPAIR ---
+            elif action == 'repair':
+                items.update_one(
+                    {'_id': ObjectId(item_id)},
+                    {'$set': {
+                        'Verfuegbar': True,
+                        'LastUpdated': datetime.datetime.now()
+                    }}
+                )
+                return True, "Item wurde repariert und ist wieder regulär verfügbar."
+
+            else:
+                return False, "Ungültige Aktion ausgewählt."
+
+    except Exception as e:
+        print(f"Error resolving repair for item {item_id}: {e}")
+        return False, "Ein Datenbankfehler ist aufgetreten."
+
 @app.route('/admin/library/items/<item_id>/invoices', methods=['GET'])
 def library_item_invoices(item_id):
     """Show all stored invoices for one specific library item."""