feat(01-02): wire init_db() into FastAPI lifespan startup

- Import init_db from imptune.db.database
- Call init_db() after DATA_DIR/DRIVERS_DIR creation in lifespan
- Database auto-initializes on every app startup via volume-mounted path

imptune/main.py

@@ -7,12 +7,14 @@ from fastapi.staticfiles import StaticFiles
 
 from imptune.api import health, pages
 from imptune.config import DATA_DIR, DRIVERS_DIR
+from imptune.db.database import init_db
 
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     os.makedirs(DATA_DIR, exist_ok=True)
     os.makedirs(DRIVERS_DIR, exist_ok=True)
+    init_db()
     yield