How to Add Rate Limiting to Your Bolt App with Upstash

# Upstash Console → Create Database
# Name: my-app-rate-limiter
# Region: US-East-1 (or closest to you)
# Copy REST URL and REST Token

Install these npm packages: @upstash/ratelimit and @upstash/redis

Create a lib/rate-limit.ts file that:
1. Imports Ratelimit from @upstash/ratelimit and Redis from @upstash/redis
2. Creates a Redis client using UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN env vars
3. Creates a rate limiter with sliding window: 10 requests per 10 seconds
4. Exports a rateLimit function that takes an identifier (like IP or user ID) and returns { success, limit, remaining }

Update my API routes to:
1. Import the rateLimit function
2. Get the user's IP from the request headers
3. Call rateLimit(ip) at the start of each handler
4. If not success, return 429 Too Many Requests with a retry-after header
5. Include remaining requests in the response headers

UPSTASH_REDIS_REST_URL=https://your-db.upstash.io
UPSTASH_REDIS_REST_TOKEN=your-token-here