Add database seeding functionality and enhance model relationships

- Implement initial data seeding for plans in the database.
- Create a new `seed_all_data` function to manage seeding process.
- Update `Sound` and `User` models to include relationships for `SoundPlayed` and `Stream`.

app/core/database.py

@@ -6,6 +6,7 @@ from sqlmodel.ext.asyncio.session import AsyncSession
 
 from app.core.config import settings
 from app.core.logging import get_logger
+from app.core.seeds import seed_all_data
 from app.models import (  # noqa: F401
     plan,
     playlist,
@@ -45,6 +46,19 @@ async def init_db() -> None:
         async with engine.begin() as conn:
             await conn.run_sync(SQLModel.metadata.create_all)
         logger.info("Database tables created successfully")
+
+        # Seed initial data
+        await seed_initial_data()
+
     except Exception:
         logger.exception("Failed to initialize database")
         raise
+
+
+async def seed_initial_data() -> None:
+    """Seed initial data into the database."""
+    logger = get_logger(__name__)
+    logger.info("Starting initial data seeding")
+
+    async with AsyncSession(engine) as session:
+        await seed_all_data(session)