fix: validate image-only uploads and respect allowed_file_types setting for journey photos

Add fileFilter to the journey photo multer config (shared by entry photo
upload and gallery upload routes):
- Rejects any non-image MIME type (including SVG which carries XSS risk)
- Checks the extension against the admin-configured allowed_file_types setting
  (same getAllowedExtensions() used by the trip file upload route)
- Returns HTTP 400 with a descriptive message on rejection

Also fix the global error handler to return err.message for 4xx responses
instead of the generic 'Internal server error', so fileFilter rejections
produce a readable error on the client.

server/src/app.ts

@@ -372,8 +372,10 @@ export function createApp(): express.Application {
     } else {
       console.error('Unhandled error:', err);
     }
-    const status = err.statusCode || 500;
-    res.status(status).json({ error: 'Internal server error' });
+    const status = err.statusCode || err.status || 500;
+    // Expose the message for client errors (4xx); keep 'Internal server error' for 5xx.
+    const message = status < 500 ? err.message : 'Internal server error';
+    res.status(status).json({ error: message });
   });
 
   return app;

server/src/routes/journey.ts

@@ -9,6 +9,7 @@ import * as svc from '../services/journeyService';
 import { db } from '../db/database';
 import { createOrUpdateJourneyShareLink, getJourneyShareLink, deleteJourneyShareLink, getPublicJourney } from '../services/journeyShareService';
 import { uploadToImmich } from '../services/memories/immichService';
+import { getAllowedExtensions } from '../services/fileService';
 
 const router = express.Router();
 
@@ -25,9 +26,26 @@ const storage = multer.diskStorage({
   },
 });
 
+const imageFilter: multer.Options['fileFilter'] = (_req, file, cb) => {
+  if (!file.mimetype.startsWith('image/') || file.mimetype.includes('svg')) {
+    const err: Error & { statusCode?: number } = new Error('Only image files are allowed');
+    err.statusCode = 400;
+    return cb(err);
+  }
+  const ext = path.extname(file.originalname).toLowerCase().replace('.', '');
+  const allowed = getAllowedExtensions().split(',').map(e => e.trim().toLowerCase());
+  if (!allowed.includes('*') && !allowed.includes(ext)) {
+    const err: Error & { statusCode?: number } = new Error(`File type .${ext} is not allowed`);
+    err.statusCode = 400;
+    return cb(err);
+  }
+  cb(null, true);
+};
+
 const upload = multer({
   storage,
   limits: { fileSize: 20 * 1024 * 1024 },
+  fileFilter: imageFilter,
 });
 
 // ── Static prefix routes (MUST come before /:id) ─────────────────────────