Complete architecture simplification: 54+ files → 37 files

- Removed 11 duplicate router files (auth.py, users.py, decks.py, card_router.py, interactions.py, user_data.py, rooms.py, games/router.py, refresh.py, card_import.py, ws.py)
- Removed duplicate core files (logging_config.py, settings.py)
- Removed unused services (card_mirror_service.py, mtgjson_loader.py, mtgjson_uploader.py)
- Removed unused schemas (proto_messages.py, protocol_constants.py)
- Created run.py startup script for simple execution
- Created app/core/config.py for unified configuration management
- Created app/core/logging.py for logging configuration
- Consolidated routers into 6 focused files (auth_router.py, users_router.py, decks_router.py, cards_router.py, user_data_router.py, games_router.py)
- Updated all imports to use consolidated model paths
- Added backward compatibility aliases in database.py
- Created SIMPLIFICATION_SUMMARY.md documentation

Architecture improvements:
- Single unified database engine with auto-detection (SQLite/PostgreSQL)
- Consolidated models into 2 files (models.py, mtg_models.py)
- Clean router structure with one file per domain
- Simplified configuration with sensible defaults
- SQLite by default for development, PostgreSQL for production

Testing:
- All imports verified working
- App loads successfully
- Ready for development and testing

backend/app/core/redis_client.py

@@ -1,26 +1,33 @@
-"""Redis client and caching layer."""
+"""Redis client and caching layer (optional)."""
 import json
 import logging
 from typing import Any, Optional
 
 import redis.asyncio as aioredis
-from app.core.settings import get_settings
+from app.core.config import get_config
 
 logger = logging.getLogger(__name__)
 
-settings = get_settings()
+config = get_config()
 
 # Redis client instance
 redis_client: Optional[aioredis.Redis] = None
 
 
-async def get_redis() -> aioredis.Redis:
-    """Get Redis client instance."""
+async def get_redis() -> Optional[aioredis.Redis]:
+    """Get Redis client instance.
+    
+    Returns None if Redis is not configured or connection fails.
+    """
     global redis_client
     if redis_client is None:
+        redis_url = getattr(config, 'REDIS_URL', None)
+        if not redis_url:
+            logger.debug("Redis not configured")
+            return None
         try:
             redis_client = aioredis.from_url(
-                settings.REDIS_URL,
+                redis_url,
                 decode_responses=True,
                 socket_connect_timeout=10,
                 socket_timeout=10,