fix: add missing SETTING_METADATA entries for db pool and upload rate limit settings

- Add db_pool_size, db_max_overflow, db_pool_timeout, db_pool_recycle fields to app/config.py
- Add upload_rate_limit_per_user, upload_rate_limit_window fields to app/config.py
- Update app/database.py to use NullPool for SQLite and QueuePool with config-driven
  pool settings for PostgreSQL/MySQL
- Add all 6 settings to SETTING_METADATA in app/utils/settings_service.py

Fixes test_all_config_settings_have_metadata failure

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/database.py

@@ -10,6 +10,7 @@ from typing import Any
 from sqlalchemy import create_engine, exc
 from sqlalchemy.engine.url import make_url
 from sqlalchemy.orm import Session, declarative_base, sessionmaker
+from sqlalchemy.pool import NullPool, QueuePool
 
 from app.config import settings
 
@@ -19,7 +20,20 @@ Base = declarative_base()
 
 # Parse the DATABASE_URL
 DB_URL = settings.database_url
-engine = create_engine(DB_URL, connect_args={"check_same_thread": False})
+_db_url = make_url(DB_URL)
+if _db_url.get_backend_name() == "sqlite":
+    # SQLite does not benefit from connection pooling; NullPool avoids contention.
+    engine = create_engine(DB_URL, connect_args={"check_same_thread": False}, poolclass=NullPool)
+else:
+    # PostgreSQL / MySQL / other: use a configurable QueuePool.
+    engine = create_engine(
+        DB_URL,
+        poolclass=QueuePool,
+        pool_size=settings.db_pool_size,
+        max_overflow=settings.db_max_overflow,
+        pool_timeout=settings.db_pool_timeout,
+        pool_recycle=settings.db_pool_recycle,
+    )
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)