feat: Initialize FastAPI AI Gateway project structure with authentication, module management, and LLM API routing.

app/core/database.py

@@ -0,0 +1,24 @@
+from sqlalchemy import create_engine
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+from app.core.config import settings
+
+# For development, we can use SQLite if DATABASE_URL is not set or for simplicity
+# But we'll follow the user's request for PostgreSQL
+SQLALCHEMY_DATABASE_URL = settings.DATABASE_URL or "sqlite:///./sql_app.db"
+
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL, 
+    # check_same_thread is only needed for SQLite
+    **({"connect_args": {"check_same_thread": False}} if "sqlite" in SQLALCHEMY_DATABASE_URL else {})
+)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+Base = declarative_base()
+
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()