fix: respect allowed_file_types setting for upload validation (#203)

The "Allowed File Types" admin setting was stored in the database but
never actually read during upload validation. Both frontend and backend
used hardcoded MIME type lists, causing video uploads (e.g. MP4) to be
rejected even when explicitly added to the setting.

Changes:
- Add getAllowedMimeTypes() to uploadSettings service that reads the
  general_allowed_file_types DB setting and converts extensions to MIME types
- Backend admin upload route now resolves allowed types from settings
  before multer processes files (via resolveAllowedTypes middleware)
- Backend gallery upload route uses dynamic allowed types from settings
- Expose allowed_file_types in public settings API for gallery clients
- Frontend PhotoUpload and UserPhotoUpload components now derive allowed
  MIME types from settings instead of hardcoded image-only lists
- Add shared fileTypes.ts utility for extension-to-MIME conversion

Closes #203

frontend/src/components/admin/PhotoUpload.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useRef } from 'react';
+import React, { useState, useRef, useMemo } from 'react';
 import { Upload, X, Image, Loader2 } from 'lucide-react';
 import { Button } from '../common';
 import { clsx } from 'clsx';
@@ -8,6 +8,7 @@ import { useQuery } from '@tanstack/react-query';
 import { categoriesService } from '../../services/categories.service';
 import { settingsService } from '../../services/settings.service';
 import { useTranslation } from 'react-i18next';
+import { extensionsToMimeTypes, extensionsToAcceptString } from '../../utils/fileTypes';
 
 interface PhotoUploadProps {
   eventId: number;
@@ -47,12 +48,22 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
     return Math.min(MAX_FILES_PER_UPLOAD_LIMIT, Math.max(1, Math.floor(parsed)));
   }, [settings]);
 
+  const allowedMimeTypes = useMemo(
+    () => extensionsToMimeTypes(settings?.general_allowed_file_types),
+    [settings?.general_allowed_file_types]
+  );
+
+  const acceptString = useMemo(
+    () => extensionsToAcceptString(settings?.general_allowed_file_types),
+    [settings?.general_allowed_file_types]
+  );
+
   const remainingSlots = Math.max(maxFilesPerUpload - selectedFiles.length, 0);
 
   const handleFileSelect = (e: React.ChangeEvent<HTMLInputElement>) => {
     const files = Array.from(e.target.files || []);
-    const imageFiles = files.filter(file => 
-      ['image/jpeg', 'image/png', 'image/webp'].includes(file.type)
+    const imageFiles = files.filter(file =>
+      allowedMimeTypes.includes(file.type)
     );
     
     // Check total file count with existing files
@@ -254,7 +265,7 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
           ref={fileInputRef}
           type="file"
           multiple
-          accept="image/jpeg,image/png,image/webp,video/mp4,video/webm,video/quicktime,video/x-msvideo"
+          accept={acceptString}
           onChange={handleFileSelect}
           className="hidden"
         />

frontend/src/components/gallery/UserPhotoUpload.tsx

@@ -1,9 +1,12 @@
-import React, { useState } from 'react';
+import React, { useState, useMemo } from 'react';
 import { Upload, X, CheckCircle } from 'lucide-react';
 import { useTranslation } from 'react-i18next';
+import { useQuery } from '@tanstack/react-query';
 import { toast } from 'react-toastify';
 import { Button } from '../common';
 import { api } from '../../config/api';
+import { publicSettingsService } from '../../services/publicSettings.service';
+import { extensionsToMimeTypes, extensionsToAcceptString } from '../../utils/fileTypes';
 
 interface UserPhotoUploadProps {
   eventId: number;
@@ -23,13 +26,28 @@ export const UserPhotoUpload: React.FC<UserPhotoUploadProps> = ({
   const [uploading, setUploading] = useState(false);
   const [uploadProgress, setUploadProgress] = useState<{ [key: string]: number }>({});
 
+  const { data: publicSettings } = useQuery({
+    queryKey: ['public-settings'],
+    queryFn: () => publicSettingsService.getPublicSettings(),
+    staleTime: 5 * 60 * 1000,
+  });
+
+  const allowedMimeTypes = useMemo(
+    () => extensionsToMimeTypes(publicSettings?.allowed_file_types),
+    [publicSettings?.allowed_file_types]
+  );
+
+  const acceptString = useMemo(
+    () => extensionsToAcceptString(publicSettings?.allowed_file_types),
+    [publicSettings?.allowed_file_types]
+  );
+
   const handleFileSelect = (e: React.ChangeEvent<HTMLInputElement>) => {
     const selectedFiles = Array.from(e.target.files || []);
-    
+
     // Validate file types
-    const allowedTypes = ['image/jpeg', 'image/png', 'image/webp'];
     const validFiles = selectedFiles.filter(file => {
-      if (!allowedTypes.includes(file.type)) {
+      if (!allowedMimeTypes.includes(file.type)) {
         toast.error(`Invalid file type: ${file.name}`);
         return false;
       }
@@ -143,7 +161,7 @@ export const UserPhotoUpload: React.FC<UserPhotoUploadProps> = ({
                     type="file"
                     className="hidden"
                     multiple
-                    accept="image/jpeg,image/png,image/webp,video/mp4,video/webm,video/quicktime,video/x-msvideo"
+                    accept={acceptString}
                     onChange={handleFileSelect}
                     disabled={uploading}
                   />