feat: add Redis storage implementation

[devin-ai-integration]

Redis Storage Implementation

This PR adds Redis as a storage backend for the rate limiter, enabling distributed rate limiting across multiple instances.

Implementation Details

• Uses Redis INCR for atomic request counting
• Sets TTL on keys to match rate limit window
• Uses Redis key prefixes to avoid collisions
• Implements proper error handling and context usage
• Includes comprehensive test suite with Redis integration tests

Configuration

Redis connection can be configured via environment variables:

REDIS_HOST=localhost    # Redis server hostname
REDIS_PORT=6379        # Redis server port
REDIS_PASSWORD=        # Optional Redis password
REDIS_DB=0            # Redis database number

Testing Instructions

1. Start Redis and the application:

docker compose up -d

2. Run tests:

docker compose exec app sh -c "cd /app && go test ./... -v"

3. Try the Redis example:

docker compose exec app sh -c "cd /app && go run examples/redis/redis.go"

Changes

• Added Redis storage implementation with TTL support
• Added Redis configuration with environment variables
• Updated docker-compose with Redis service
• Added Redis example implementation
• Added Redis tests with proper cleanup
• Updated documentation with Redis usage

Testing Done

• All tests passing including Redis integration tests
• Redis example working with Docker Compose
• Proper error handling and cleanup implemented
• Verified concurrent request handling
• Tested key expiration and cleanup

Link to Devin run: https://app.devin.ai/sessions/f6c48165523740d4ab8e798b0b34531b
Requested by: Wesley

[devin-ai-integration]

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