I need to add a credit system to track AI usage in my app with Supabase:

Database schema needed:
1. Add to user profiles table:
   - account_type (free/paid/cancelled)
   - credits_remaining (integer, default based on tier)
   - credits_used_this_month (integer, default 0)
   - last_credit_reset (timestamp)
   - subscription_start_date (timestamp)

2. Create usage_log table:
   - user_id (foreign key to profiles)
   - credits_used (integer)
   - action_type (text: "ai_generation", "api_call", etc)
   - timestamp (when the usage occurred)

Credit rules:
- Free users: 5 credits total, no reset
- Paid users: [INSERT YOUR CALCULATED LIMIT] credits, reset monthly on subscription anniversary
- Each AI request costs 1 credit
- Block requests when credits_remaining = 0
- Show usage dashboard with remaining/used counts

Please create this database structure and the logic to handle credit deduction and monthly resets.