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/services/deck_suggestion_service.py

@@ -4,9 +4,8 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select, or_, and_, func, case
 from sqlalchemy.orm import selectinload
 
-from app.models.user_deck import UserDeck, UserDeckCard, CardSuggestion
-from app.models.mtg_models import MtgCard
-from app.models.mirror_models import MtgCardMirror
+from app.models.models import UserDeck, UserDeckCard, CardSuggestion
+from app.models.mtg_models import MtgCard, MtgCardMirror
 from app.services.fuzzy_card_matcher import FuzzyCardMatcher