Add Rate Limiting to Lovable App

Add rate limiting to my Lovable app's Edge Functions.

REQUIREMENTS:
1. Create a rate limiting utility that tracks requests per IP or user ID using a Supabase table.
2. Implement sliding window rate limiting: allow N requests per M-second window (e.g., 10 requests per 60 seconds).
3. Wrap existing Edge Functions with the rate limiter as middleware.
4. When rate limited, return HTTP 429 with headers: X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset, and Retry-After.
5. Show a user-friendly error message on the client: "Too many requests. Please try again in X seconds."
6. Add different rate limits per endpoint (e.g., auth endpoints: 5/min, API endpoints: 30/min, public endpoints: 60/min).
7. Create a cleanup function that runs periodically to delete expired rate limit entries.
8. Log rate limit hits for monitoring abuse patterns.

DATABASE:
- "rate_limits" table: id, identifier (IP or user_id), endpoint, request_count, window_start, created_at
- Index on (identifier, endpoint, window_start) for fast lookups.
- Consider using pg_cron for automatic cleanup of old entries.

SECURITY:
- Use IP-based limiting for unauthenticated endpoints.
- Use user-based limiting for authenticated endpoints.
- Don't expose internal rate limit logic to clients.