refactor: fix P0/P1/P2 security and performance issues

P0 fixes:
- CORS: replace wildcard methods/headers with configurable lists
- deps.py: remove unsafe global _warned_unset variable

P1 fixes:
- http_client: read default timeout from Settings
- bzzoiro: replace sync urllib with async httpx
- bzzoiro: normalize validation failures use warning level only
- db pool: read pool config from Settings (default 5+10)
- backtest: add asyncio.Semaphore(8) for concurrent execution
- predict/context_builder: add backtest parameter for cutoff buffer

P2 improvements:
- injuries: enforce int conversion for player_id/fixture_id
- injuries: use system temp dir for cache
- utils.py: extract shared actual_1x2/is_correct_1x2
- validation: downgrade 1x2 mismatch log to debug
- docker-compose: use env vars for all credentials
- .env.example: add POSTGRES_USER/PASSWORD/PORT, API_PORT

src/db/base.py

@@ -17,8 +17,10 @@ engine = create_async_engine(
     settings.DATABASE_URL,
     echo=False,
     pool_pre_ping=True,
-    pool_size=10,
-    max_overflow=20,
+    pool_size=settings.DB_POOL_SIZE,
+    max_overflow=settings.DB_MAX_OVERFLOW,
+    pool_timeout=settings.DB_POOL_TIMEOUT,
+    pool_recycle=settings.DB_POOL_RECYCLE,
 )
 
 AsyncSessionLocal = async_sessionmaker(