feat(student-cards): add class-specific PDF export with dynamic dropdown

- Implement /student_card_class_barcode_download route to filter student cards by class
- Dynamically extract unique class names from the database for frontend selection
- Update student_cards_admin.html to replace the text input with a class selection dropdown

Web/templates/student_cards_admin.html

@@ -232,6 +232,16 @@
             <h1>📚 Bibliotheksausweise (Bibliothek)</h1>
         </div>
         <div class="export-buttons">
+            <form method="GET" action="{{ url_for('student_card_class_barcode_download') }}" style="display: inline-flex; gap: 5px; align-items: center; background: white; padding: 2px; border-radius: 4px; border: 1px solid #ddd;">
+                <select name="class_name" required style="border: none; padding: 8px; outline: none; font-size: 14px; background: transparent; cursor: pointer;">
+                    <option value="" disabled selected>-- Klasse wählen --</option>
+                    {% for cls in available_classes %}
+                        <option value="{{ cls }}">{{ cls }}</option>
+                    {% endfor %}
+                </select>
+                <button type="submit" class="btn-print" style="background: #17a2b8; padding: 8px 12px; margin: 0;">📤 PDF</button>
+            </form>
+
             <a href="{{ url_for('student_card_barcode_download') }}" class="btn-print" style="background: #28a745;">📥 Alle Ausweise (PDF)</a>
             <a href="{{ url_for('library_admin') }}" class="btn btn-primary">← Zur Bibliotheks-Upload</a>
         </div>

Web/templates/upload_admin.html

@@ -836,7 +836,7 @@
                             <!-- Options will be loaded by JavaScript -->
                         </select>
                     </div>
-                    <div class="formupload_admin-group">
+                    <div class="form-group">
                         <label for="filter2-4">Wert 4:</label>
                         <select id="filter2-4" name="filter2" class="filter-dropdown-select">
                             <option value="">-- Optional --</option>
@@ -876,11 +876,11 @@
             </div>
 
 
-            <!-- Image upload (hidden for library mode) -->
+            <!-- Image upload -->
             <div class="form-group">
-                <label for="images">Bilder/Videos:</label>
-                <input type="file" id="images" name="images" accept=".jpg, .jpeg, .png, .gif, .mp4, .mov, .avi, .mkv, .webm, .flv, .m4v, .3gp" multiple>
-                <div class="allowed-formats">Erlaubte Formate: JPG, JPEG, PNG, GIF, MP4, MOV, AVI, MKV, WEBM, FLV, M4V, 3GP</div>
+                <label for="images">Bilder:</label>
+                <input type="file" id="images" name="images" accept=".jpg, .jpeg, .png, .gif" multiple>
+                <div class="allowed-formats">Erlaubte Formate: JPG, JPEG, PNG, GIF</div>
                 <!-- Add image preview area -->
                 <div class="image-preview-container" id="image-preview-container"></div>
             </div>
@@ -1857,28 +1857,25 @@
     function setupImagePreview() {
         const imageInput = document.getElementById('images');
         const previewContainer = document.getElementById('image-preview-container');
-        
+
         if (imageInput && previewContainer) {
             imageInput.addEventListener('change', function(e) {
                 previewContainer.innerHTML = '';
-                
+
                 const files = e.target.files;
-                
-                // Validate file types before preview
-                const allowedTypes = ['image/jpeg', 'image/jpg', 'image/png', 'image/gif', 
-                                    'video/mp4', 'video/quicktime', 'video/x-msvideo', 'video/x-matroska', 
-                                    'video/webm', 'video/x-flv', 'video/mp4', 'video/3gpp'];
-                let hasInvalidFile = false;
-                
+
+                // Validate file types before preview (Strictly Images)
+                const allowedTypes = ['image/jpeg', 'image/jpg', 'image/png', 'image/gif'];
+
                 for (let i = 0; i < files.length; i++) {
                     if (!allowedTypes.includes(files[i].type)) {
-                        hasInvalidFile = true;
                         // Clear the file input to prevent submission
                         imageInput.value = '';
-                        previewContainer.innerHTML = '<div class="error-message">Fehler: Datei "' + files[i].name + '" hat ein nicht unterstütztes Format. Erlaubte Formate: JPG, JPEG, PNG, GIF, MP4, MOV, AVI, MKV, WEBM, FLV, M4V, 3GP</div>';
+                        previewContainer.innerHTML = '<div class="error-message">Fehler: Datei "' + files[i].name + '" hat ein nicht unterstütztes Format. Erlaubte Formate: JPG, JPEG, PNG, GIF</div>';
                         return; // Stop processing
                     }
                 }
+
                 for (let i = 0; i < files.length; i++) {
                     const file = files[i];
                     if (file.type.startsWith('image/')) {
@@ -1893,17 +1890,6 @@
                             previewContainer.appendChild(preview);
                         };
                         reader.readAsDataURL(file);
-                    } else if (file.type.startsWith('video/')) {
-                        const preview = document.createElement('div');
-                        preview.className = 'image-preview video-preview';
-                        preview.innerHTML = `
-                            <div class="video-placeholder">
-                                <div class="video-icon">🎥</div>
-                                <div class="video-name">${file.name}</div>
-                            </div>
-                            <button type="button" class="remove-image" onclick="removeImagePreview(this, ${i})">×</button>
-                        `;
-                        previewContainer.appendChild(preview);
                     }
                 }
             });