Working device manager, added folders for better organization.

services/device_manager/database.py

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+"""
+Database session management for FastAPI with SQLAlchemy.
+
+Uses dependency injection pattern for database sessions.
+"""
+from collections.abc import Generator
+from contextlib import contextmanager
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session, sessionmaker
+
+from config import config
+
+# Create engine with connection pooling
+engine = create_engine(
+    config.DATABASE_URL,
+    pool_pre_ping=True,
+    pool_size=5,
+    max_overflow=10,
+    echo=False,
+)
+
+SessionLocal = sessionmaker(
+    autocommit=False,
+    autoflush=False,
+    bind=engine,
+)
+
+
+def get_db() -> Generator[Session]:
+    """
+    FastAPI dependency that provides a database session.
+
+    Usage in endpoints:
+        @app.post("/devices")
+        async def create_device(db: Session = Depends(get_db)):
+            device = Device(...)
+            db.add(device)
+            db.commit()
+            return device
+
+    The session is automatically closed after the request completes.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+@contextmanager
+def get_db_context():
+    """
+    Context manager for database sessions outside of FastAPI endpoints.
+    Usage:
+        with get_db_context() as db:
+            device = db.query(Device).first()
+    """
+    db = SessionLocal()
+    try:
+        yield db
+        db.commit()
+    except Exception:
+        db.rollback()
+        raise
+    finally:
+        db.close()
+
+
+def check_db_connection() -> bool:
+    """
+    Check if database connection is working.
+
+    Returns:
+        True if connection successful, False otherwise
+    """
+    try:
+        with engine.connect() as conn:
+            conn.execute("SELECT 1")
+        return True
+    except Exception as e:
+        print(f"Database connection failed: {e}")
+        return False