fix: prevent photo corruption during upload and add batch processing improvements

- Remove async functions from multer callbacks (primary corruption cause)
- Implement temp directory upload approach with proper cleanup
- Add comprehensive file integrity validation before processing
- Fix batch upload category assignment and photo naming
- Add automatic cleanup service for orphaned temp uploads
- Enhance error handling with better corruption detection
- Add fix-temp-photos script to repair existing temporary files
- Update file watcher to ignore temp upload files

Fixes issues with:
- Corrupted photos showing only partial images
- Photos retaining temp_ names after upload
- Category assignments lost during batch uploads
- Incomplete file uploads causing "Premature end of input" errors

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/server.js

@@ -218,6 +218,14 @@ async function startServer() {
     const { initializeCleanupJob } = require('./src/utils/authSecurity');
     initializeCleanupJob();
     
+    // Initialize temp upload cleanup job
+    const { cleanupTempUploads } = require('./src/utils/cleanupTempUploads');
+    // Run cleanup on startup
+    cleanupTempUploads();
+    // Schedule periodic cleanup every hour
+    setInterval(cleanupTempUploads, 60 * 60 * 1000);
+    logger.info('Temp upload cleanup scheduled');
+    
     // Start file watcher
     startFileWatcher();