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>

config.py

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+import os
+
+class Config:
+    """Application configuration loaded from environment variables."""
+    SECRET_KEY = os.environ.get('SECRET_KEY', 'dev-secret-key-change-in-production')
+    NEXTCLOUD_URL = os.environ.get('NEXTCLOUD_URL', 'https://nextcloud.sdanywhere.com')
+    
+    # Session configuration
+    SESSION_TYPE = 'filesystem'
+    SESSION_FILE_DIR = '/tmp/flask_session'
+    SESSION_PERMANENT = False
+    SESSION_USE_SIGNER = True
+    SESSION_COOKIE_SAMESITE = 'Strict'
+    SESSION_COOKIE_HTTPONLY = True
+    SESSION_COOKIE_SECURE = True  # Set to False for local development
+    
+    # Upload configuration
+    MAX_CONTENT_LENGTH = 50 * 1024 * 1024  # 50MB max upload
+    
+    # Development mode
+    DEBUG = os.environ.get('FLASK_DEBUG', 'False').lower() == 'true'
+
+class DevelopmentConfig(Config):
+    """Development-specific configuration."""
+    DEBUG = True
+    SESSION_COOKIE_SECURE = False  # Allow HTTP in development
+
+class ProductionConfig(Config):
+    """Production-specific configuration."""
+    DEBUG = False
+    
+    # Ensure these are set in production
+    def __init__(self):
+        super().__init__()
+        if self.SECRET_KEY == 'dev-secret-key-change-in-production':
+            raise ValueError("SECRET_KEY must be set in production!")
+
+# Configuration dictionary
+config = {
+    'development': DevelopmentConfig,
+    'production': ProductionConfig,
+    'default': DevelopmentConfig
+}