Add NextSnap PWA with photo gallery viewer and continuous capture

Offline-first photo capture app for Nextcloud with:
- Camera capture with continuous mode (auto-reopens after each photo)
- File browser with fullscreen image gallery, swipe navigation, and rename
- Upload queue with background sync engine
- Admin panel for Nextcloud user management
- Service worker for offline-first caching (v13)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

run.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python3
+"""Development server runner."""
+from app import create_app
+import os
+
+if __name__ == '__main__':
+    app = create_app('development')
+    port = int(os.environ.get('PORT', 5000))
+    app.run(host='0.0.0.0', port=port, debug=True)