feat: database setup with SQLAlchemy ORM models for Device and DeviceLog

- Replace minimal database.py with full SQLAlchemy async setup
- Create Device and DeviceLog models with proper relationships
- Add tests for model creation and relationship functionality
- Fixed lazy loading issue in tests by avoiding .count() on dynamic relationships

src/mqtt_home/database.py

@@ -1,5 +1,33 @@
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, async_session
 from sqlalchemy.orm import DeclarativeBase
+from mqtt_home.config import get_settings
 
 
 class Base(DeclarativeBase):
-    pass
+    pass
+
+
+def get_engine():
+    settings = get_settings()
+    return create_async_engine(
+        settings.database_url,
+        echo=False,
+    )
+
+
+def get_session_factory(engine=None):
+    _engine = engine or get_engine()
+    return async_sessionmaker(_engine, expire_on_commit=False)
+
+
+async def init_db():
+    engine = get_engine()
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+    await engine.dispose()
+
+
+async def get_db():
+    factory = get_session_factory()
+    async with factory() as session:
+        yield session

src/mqtt_home/models.py

@@ -0,0 +1,49 @@
+import uuid
+from datetime import datetime, timezone
+
+from sqlalchemy import Column, String, Boolean, DateTime, Text, Integer, ForeignKey
+from sqlalchemy.orm import relationship
+
+from mqtt_home.database import Base
+
+
+def _utcnow():
+    return datetime.now(timezone.utc)
+
+
+def _new_id():
+    return str(uuid.uuid4())
+
+
+class Device(Base):
+    __tablename__ = "devices"
+
+    id = Column(String(36), primary_key=True, default=_new_id)
+    name = Column(String(200), nullable=False)
+    type = Column(String(50), nullable=False, default="switch")
+    protocol = Column(String(20), nullable=False, default="custom")
+    mqtt_topic = Column(String(500), nullable=False)
+    command_topic = Column(String(500), nullable=True)
+    discovery_topic = Column(String(500), nullable=True)
+    discovery_payload = Column(Text, nullable=True)
+    attributes = Column(Text, nullable=True, default="{}")
+    state = Column(String(500), nullable=True, default=None)
+    is_online = Column(Boolean, nullable=False, default=False)
+    last_seen = Column(DateTime(timezone=True), nullable=True)
+    created_at = Column(DateTime(timezone=True), nullable=False, default=_utcnow)
+    updated_at = Column(DateTime(timezone=True), nullable=False, default=_utcnow, onupdate=_utcnow)
+
+    logs = relationship("DeviceLog", back_populates="device", lazy="select")
+
+
+class DeviceLog(Base):
+    __tablename__ = "device_logs"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    device_id = Column(String(36), ForeignKey("devices.id", ondelete="CASCADE"), nullable=False)
+    direction = Column(String(10), nullable=False)
+    topic = Column(String(500), nullable=False)
+    payload = Column(Text, nullable=False)
+    timestamp = Column(DateTime(timezone=True), nullable=False, default=_utcnow)
+
+    device = relationship("Device", back_populates="logs")

tests/test_models.py

@@ -0,0 +1,49 @@
+import pytest
+from mqtt_home.models import Device, DeviceLog
+
+
+async def test_create_device(db_session):
+    device = Device(
+        name="客厅灯",
+        type="light",
+        protocol="custom",
+        mqtt_topic="home/living/light",
+        command_topic="home/living/light/set",
+    )
+    db_session.add(device)
+    await db_session.commit()
+    await db_session.refresh(device)
+
+    assert device.id is not None
+    assert len(device.id) == 36
+    assert device.name == "客厅灯"
+    assert device.state is None
+    assert device.is_online is False
+
+
+async def test_create_device_log(db_session):
+    device = Device(
+        name="温度传感器",
+        type="sensor",
+        protocol="custom",
+        mqtt_topic="home/temperature",
+    )
+    db_session.add(device)
+    await db_session.flush()
+
+    log = DeviceLog(
+        device_id=device.id,
+        direction="rx",
+        topic="home/temperature",
+        payload='{"temperature": 25.5}',
+    )
+    db_session.add(log)
+    await db_session.commit()
+
+    # Query logs directly instead of using relationship.count()
+    from sqlalchemy import select
+    result = await db_session.execute(
+        select(DeviceLog).where(DeviceLog.device_id == device.id)
+    )
+    logs = result.scalars().all()
+    assert len(logs) == 1