feat: implement feedback filter for liked/favorited photos (Issue #17)

Implemented Feature Request 1 from github.com/the-luap/picpeak/issues/17:
- Added filter functionality to display only liked or favorited photos
- Integrated feedback filter directly into PhotoFilterBar component
- Implemented responsive design with proper mobile/tablet/desktop layouts
- Filter only shows when feedback is enabled for the gallery
- Added proper count display for liked and favorited photos

Improvements:
- Fixed responsive breakpoints (mobile <768px, tablet 768-1023px, desktop ≥1024px)
- Feedback filter shows inline with categories on desktop with vertical divider
- On mobile/tablet, filter appears below categories to prevent layout issues
- Added horizontal scrolling for category buttons to prevent cut-off

Code cleanup:
- Removed all debug console.log statements from production code
- Removed test route from backend gallery.js
- Cleaned up unnecessary logging in frontend components

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

Co-Authored-By: Claude <[email protected]>

frontend/src/i18n/locales/en.json

@@ -134,6 +134,12 @@
     "sortByName": "Sort by Name", 
     "sortBySize": "Sort by Size",
     "allPhotos": "All Photos",
+    "filter": "Filter",
+    "feedbackFilter": "Feedback Filter",
+    "all": "All",
+    "liked": "Liked",
+    "favorited": "Favorited",
+    "favorites": "Favorites",
     "downloadSelected": "Download Selected",
     "shareGallery": "Share Gallery",
     "needHelp": "Need help? Contact us at",