feat(school-logo): implement logo upload functionality and update school settings UI

Web/templates/admin_school_settings.html

@@ -32,7 +32,7 @@
                 <h2>Schuldaten</h2>
             </div>
             <div class="card-body">
-                <form method="POST" action="{{ url_for('admin_school_settings') }}">
+                <form method="POST" action="{{ url_for('admin_school_settings') }}" enctype="multipart/form-data">
                     <div class="form-row">
                         <div class="form-group">
                             <label for="name">Schulname *</label>
@@ -66,9 +66,9 @@
                     </div>
 
                     <div class="form-group">
-                        <label for="logo_path">Logo-Pfad oder Dateiname</label>
-                        <input type="text" id="logo_path" name="logo_path" value="{{ school_info.logo_path or '' }}" placeholder="optional, z. B. static/img/schullogo.png">
-                        <small>Der Logo-Pfad wird gespeichert und kann später für den PDF-Briefkopf verwendet werden.</small>
+                        <label for="logo_upload">Schullogo hochladen</label>
+                        <input type="file" id="logo_upload" name="logo_upload" accept=".png,.jpg,.jpeg,.gif,.webp,.svg,image/*">
+                        <small>Upload ersetzt das bisherige Logo. Wenn kein neues Logo gewählt wird, bleibt das aktuelle erhalten.</small>
                     </div>
 
                     <div class="actions-row">
@@ -84,6 +84,13 @@
                 <h2>Aktuelle Vorschau</h2>
             </div>
             <div class="card-body">
+                {% if school_info.logo_path %}
+                <div style="margin-bottom:16px; padding:12px; border:1px solid #e5e7eb; border-radius:10px; background:#fff;">
+                    <div style="font-weight:700; margin-bottom:8px; color:#374151;">Aktuelles Logo</div>
+                    <img src="{{ url_for('uploaded_file', filename=school_info.logo_path) }}" alt="Aktuelles Schullogo" style="max-width:100%; max-height:180px; object-fit:contain; display:block;">
+                    <div style="margin-top:8px; font-size:0.85rem; color:#6b7280; word-break:break-word;">{{ school_info.logo_path }}</div>
+                </div>
+                {% endif %}
                 <p><strong>Schulname:</strong> {{ school_info.name or 'Nicht gesetzt' }}</p>
                 <p><strong>Adresse:</strong> {{ school_info.address or 'Nicht gesetzt' }}</p>
                 <p><strong>Schulnummer:</strong> {{ school_info.school_number or 'Nicht gesetzt' }}</p>