fix: implement proper database connection context manager

- Created DBConnection class to manage database connections
- Each connection is now properly created and closed
- Removed global connection pool to fix thread issues

backend/main.py

@@ -105,17 +105,27 @@ ha_mqtt = HomeAssistantMQTT()
 DB_PATH = "gatekeeper.db"  # Database file path
 
 # Database connection handling
-async def get_db():
+class DBConnection:
+    def __init__(self):
+        self.db = None
+
+    async def __aenter__(self):
+        self.db = await aiosqlite.connect(DB_PATH)
+        self.db.row_factory = aiosqlite.Row
+        return self.db
+
+    async def __aexit__(self, exc_type, exc_val, exc_tb):
+        await self.db.close()
+
+def get_db():
     """Get a new database connection"""
-    db = await aiosqlite.connect(DB_PATH)
-    db.row_factory = aiosqlite.Row
-    return db
+    return DBConnection()
 
 # Set up MQTT event logging
 async def log_mqtt_event(action: str, success: bool = True):
     """Log MQTT events to the database and log file"""
     logger.info(f"MQTT Event - {action} (Success: {success})")
-    async with await get_db() as db:
+    async with get_db() as db:
         await db.execute(
             "INSERT INTO events (timestamp, action, source, success) VALUES (?, ?, ?, ?)",
             (datetime.utcnow().isoformat(), action, "MQTT", success)
@@ -188,7 +198,7 @@ async def update_gate_status():
                     logger.info(f"Gate status changed to: {'open' if current_status else 'closed'}")
                     logger.debug("Updating database with new status")
                     
-                    async with await get_db() as db:
+                    async with get_db() as db:
                         await db.execute(
                             "INSERT INTO gate_status (timestamp) VALUES (?)",
                             (timestamp.isoformat(),)
@@ -258,7 +268,7 @@ async def check_auto_close():
                         logger.warning(f"Gate has been open for {time_open:.1f} seconds, auto-closing")
                         timestamp = current_time.isoformat()
                         
-                        async with await get_db() as db:
+                        async with get_db() as db:
                             await db.execute(
                                 "INSERT INTO events (timestamp, action, source, success) VALUES (?, ?, ?, ?)",
                                 (timestamp, "auto-close", "system", True)
@@ -314,7 +324,7 @@ async def trigger():
         current_status = GPIO.input(settings.gpio.statusPin) == GPIO.HIGH
         
         # Log event
-        async with await get_db() as db:
+        async with get_db() as db:
             await db.execute(
                 "INSERT INTO events (timestamp, action, source, success) VALUES (?, ?, ?, ?)",
                 (timestamp, "trigger gate", "api", success)
@@ -333,7 +343,7 @@ async def get_status():
         settings = app.state.current_settings or Settings()
         is_open = GPIO.input(settings.gpio.statusPin) == GPIO.HIGH
         
-        async with await get_db() as db:
+        async with get_db() as db:
             cursor = await db.execute(
                 "SELECT timestamp FROM gate_status ORDER BY timestamp DESC LIMIT 1"
             )
@@ -348,7 +358,7 @@ async def get_status():
 @app.get("/api/events")
 async def get_events(limit: int = 10, offset: int = 0):
     """Get recent gate events with pagination"""
-    async with await get_db() as db:
+    async with get_db() as db:
         db.row_factory = aiosqlite.Row
         
         # Get total count
@@ -375,7 +385,7 @@ async def get_events(limit: int = 10, offset: int = 0):
 @app.get("/api/settings")
 async def get_settings():
     """Get current settings"""
-    async with await get_db() as db:
+    async with get_db() as db:
         cursor = await db.execute("SELECT key, value FROM settings")
         rows = await cursor.fetchall()
         settings = {}
@@ -408,7 +418,7 @@ async def get_settings():
 async def update_settings(settings: Settings):
     """Update settings"""
     try:
-        async with await get_db() as db:
+        async with get_db() as db:
             # Update each setting
             for key, value in settings.dict().items():
                 await db.execute(
@@ -458,7 +468,7 @@ async def update_settings(settings: Settings):
         return {"success": True}
     except Exception as e:
         # Log failure event
-        async with await get_db() as db:
+        async with get_db() as db:
             await db.execute(
                 "INSERT INTO events (timestamp, action, source, success) VALUES (?, ?, ?, ?)",
                 (
@@ -503,7 +513,7 @@ def setup_gpio():
 # Database functions
 async def init_db():
     """Initialize the SQLite database"""
-    async with await get_db() as db:
+    async with get_db() as db:
         # Create events table
         await db.execute("""
             CREATE TABLE IF NOT EXISTS events (