Fix issue #22: Gallery filter counts disappearing and upload errors

This commit comprehensively addresses the persistent issues reported in #22:

1. Gallery Filter Bug - Counts Disappearing
   - Root cause: Frontend fetched filtered photos from backend, then
     calculated counts from already-filtered data
   - Fix: Always fetch ALL photos, apply filtering client-side only
   - Benefits: Counts always accurate, filters work correctly in combo
   - Changed: frontend/src/components/gallery/GalleryView.tsx:76

2. Upload ENOENT Errors
   - Root cause: /tmp/uploads/ directory assumed to exist
   - Fix: Verify and create temp directory before multer initialization
   - Changed: backend/src/routes/gallery.js:814-825

3. Upload "Not Iterable" Errors
   - Root cause: normalizeFiles() didn't handle null/edge cases
   - Fix: Enhanced error handling with try-catch and graceful degradation
   - Changed: backend/src/services/photoProcessor.js:10-52

4. Enhanced Upload Debugging
   - Added file existence verification before copy operations
   - Improved temp file cleanup (properly handle ENOENT)
   - Comprehensive error logging with full context
   - Changed: backend/src/services/photoProcessor.js:108-233

Technical Details:
- Gallery filtering now entirely client-side (simpler architecture)
- Upload error messages now include full diagnostic context
- Temp file cleanup handles ENOENT gracefully (expected scenario)
- All fixes preserve backward compatibility

Testing:
- Gallery filters: Verify counts stay visible when filtering
- Uploads: Test single/batch uploads, check temp cleanup
- Logs: Verify detailed error context on failures

See ISSUE_22_FIX_SUMMARY.md for complete analysis and testing guide.

Fixes #22

backend/src/routes/gallery.js

@@ -800,22 +800,35 @@ router.get('/:slug/stats', verifyGalleryAccess, async (req, res) => {
 router.post('/:eventId/upload', verifyGalleryAccess, async (req, res) => {
   try {
     const eventId = parseInt(req.params.eventId);
-    
+
     // Verify the event matches the token
     if (req.event.id !== eventId) {
       return res.status(403).json({ error: 'Access denied' });
     }
-    
+
     // Check if user uploads are allowed
     if (!req.event.allow_user_uploads) {
       return res.status(403).json({ error: 'User uploads are not allowed for this event' });
     }
-    
+
+    // Ensure temp upload directory exists
+    const fs = require('fs');
+    const tempUploadDir = '/tmp/uploads/';
+    if (!fs.existsSync(tempUploadDir)) {
+      try {
+        fs.mkdirSync(tempUploadDir, { recursive: true, mode: 0o755 });
+        logger.info('Created temp upload directory:', tempUploadDir);
+      } catch (mkdirErr) {
+        logger.error('Failed to create temp upload directory:', mkdirErr);
+        return res.status(500).json({ error: 'Server configuration error: unable to create upload directory' });
+      }
+    }
+
     // Import multer and photo processing
     const multer = require('multer');
-    const upload = multer({ 
-      dest: '/tmp/uploads/',
-      limits: { 
+    const upload = multer({
+      dest: tempUploadDir,
+      limits: {
         fileSize: 50 * 1024 * 1024, // 50MB
         files: 10 // Max 10 files at once
       },