Fix critical issues: gallery authentication and photo duplication

- Fix gallery-specific authentication for images
  - Update AuthenticatedImage component to use gallery-specific tokens
  - Add isGallery prop to distinguish between admin and gallery contexts
  - Update PhotoGrid and PhotoLightbox to pass isGallery prop

- Fix photo duplication issue in fileWatcher service
  - Add check to prevent duplicate photo entries when backend restarts
  - File watcher now verifies if photo exists before inserting
  - Cleaned up 176 duplicate photos from database

These fixes resolve:
1. Gallery images not loading due to auth token errors
2. Photo count increasing without new uploads due to duplicates

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

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

backend/src/services/fileWatcher.js

@@ -63,17 +63,26 @@ async function processNewPhoto(filePath) {
   // Calculate relative thumbnail path
   const relativeThumbPath = thumbnailPath; // thumbnailPath is already relative to storage root
   
-  // Add to database
-  await db('photos').insert({
-    event_id: event.id,
-    filename: path.basename(filePath),
-    path: relativePath,
-    thumbnail_path: relativeThumbPath,
-    type: photoType,
-    size_bytes: stats.size
-  });
+  // Check if photo already exists
+  const existingPhoto = await db('photos')
+    .where({ event_id: event.id, filename: path.basename(filePath) })
+    .first();
   
-  logger.info(`Added new photo: ${relativePath}`);
+  if (!existingPhoto) {
+    // Add to database
+    await db('photos').insert({
+      event_id: event.id,
+      filename: path.basename(filePath),
+      path: relativePath,
+      thumbnail_path: relativeThumbPath,
+      type: photoType,
+      size_bytes: stats.size
+    });
+    
+    logger.info(`Added new photo: ${relativePath}`);
+  } else {
+    logger.debug(`Photo already exists: ${relativePath}`);
+  }
 }
 
 async function removePhoto(filePath) {