User: Add rate limiting to the API endpoints. [COMPLEXITY: MEDIUM] [MODE: PIPELINE] [REASON: Requires modifying 3 files — middleware, route handlers, and config] Step 1: Read current middleware stack → identify insertion point Step 2: Implement rate-limit middleware using existing dependencies Step 3: Apply middleware to target route groups Step 4: Add config values (limit, window, key strategy) Step 1 complete. Proceeding to Step 2. [...] Pipeline complete. 4 steps executed. Files changed: middleware/index.ts, routes/api.ts, config/limits.ts.