Add landing page, referral system, usage quotas, search API management, and yearly pricing

- Separate workspace landing from login for better UX
- Referral system rewards both parties with Pro days
- Quota enforcement prevents abuse without breaking endpoints
- 7-day free trial with auto-downgrade on expiry
- Admin-managed search provider config (SearXNG, Bing)
- 15% discount on annual subscriptions
- MCP search server wrapping opencode search
- Fix discovery module field name mismatch causing 422

backend/app/api/v1/product.py

@@ -4,6 +4,7 @@ from typing import Optional, List
 from app.database import get_db
 from app.services.product import ProductService
 from app.services import export
+from app.services.usage import UsageService
 from app.api.v1.deps import get_current_user_id
 from pydantic import BaseModel
 import io
@@ -175,8 +176,13 @@ async def create_product(
     user_id: str = Depends(get_current_user_id),
     db: AsyncSession = Depends(get_db),
 ):
+    usage = UsageService(db)
+    ok, msg = await usage.check_quota(user_id, "create_product")
+    if not ok:
+        raise HTTPException(status_code=429, detail=msg)
     service = ProductService(db)
     product = await service.create_product(user_id, data.dict())
+    await usage.record_usage(user_id, "create_product")
     return product