feat: implement server-side rate limiting for API routes

[anxkhn]

Problem Description

API routes lack rate limiting, making them vulnerable to abuse and DoS attacks.

Context

Rate limiting protects server resources and ensures fair usage.

Files to Investigate

• src/app/api/events/route.ts - Events API
• src/app/api/events/upvote/route.ts - Upvote API

Expected Behavior

API should limit requests per IP/user within a time window.

Acceptance Criteria

• Implement rate limiting middleware
• Rate limit by IP address
• Return 429 status when exceeded
• Include rate limit headers
• Test rate limiting works

Suggested Approach

Create a rate limiting middleware or use a library. Store request counts in memory.

Difficulty: Hard

Estimated time: 3-6 hours
Prerequisites: API security, middleware patterns
Learning outcomes: Rate limiting, API protection