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/seeds.py

@@ -0,0 +1,65 @@
+"""Database seeding functionality."""
+
+from sqlmodel import select
+from sqlmodel.ext.asyncio.session import AsyncSession
+
+from app.core.logging import get_logger
+from app.models.plan import Plan
+
+logger = get_logger(__name__)
+
+
+async def seed_plans(session: AsyncSession) -> None:
+    """Seed initial plan data."""
+    logger.info("Seeding plan data")
+
+    # Check if plans already exist
+    existing_plans = await session.exec(select(Plan))
+    if existing_plans.first():
+        logger.info("Plans already exist, skipping seeding")
+        return
+
+    # Define initial plans
+    initial_plans = [
+        Plan(
+            code="free",
+            name="Free Plan",
+            description="Basic free plan with limited features",
+            credits=25,
+            max_credits=75,
+        ),
+        Plan(
+            code="premium",
+            name="Premium Plan",
+            description="Premium plan with more features",
+            credits=50,
+            max_credits=150,
+        ),
+        Plan(
+            code="pro",
+            name="Pro Plan",
+            description="Pro plan with unlimited features",
+            credits=100,
+            max_credits=300,
+        ),
+    ]
+
+    # Add plans to session
+    for plan in initial_plans:
+        session.add(plan)
+
+    await session.commit()
+    logger.info("Successfully seeded %d plans", len(initial_plans))
+
+
+async def seed_all_data(session: AsyncSession) -> None:
+    """Seed all initial data."""
+    logger.info("Starting data seeding")
+
+    try:
+        await seed_plans(session)
+        logger.info("Data seeding completed successfully")
+    except Exception:
+        logger.exception("Failed to seed data")
+        await session.rollback()
+        raise