feat: Add support for local Redis caching

[cvaz1306]

This change introduces the capability to use a local or self-hosted Redis instance for caching responses, in addition to the existing Upstash Redis and Cloudflare KV options.

Modifications include:

• Updated src/env.ts to include LOCAL_REDIS_URL, LOCAL_REDIS_PORT, and LOCAL_REDIS_PASSWORD environment variable definitions.
• Modified src/cache.ts to use ioredis for connecting to a local Redis instance. The caching preference order is now Upstash Redis, then Local Redis, then Cloudflare KV.
• Added ioredis to package.json dependencies and @types/ioredis to devDependencies.
• Updated wrangler.toml with instructions and examples for configuring local Redis via environment variables/secrets or .dev.vars.
• Updated README.md to document the new local Redis feature, including configuration instructions and the cache priority order.