Desc: Enhance existing rateLimiter.ts (currently 60 req/60s per IP). Add per-user rate limiting keyed by wallet address (30 req/60s). Add separate limit for prepare-* endpoints (10 req/10s) to prevent burst traffic. Reference dca-service pattern: tiered limits by endpoint type. Files: backend/src/middleware/rateLimiter.ts.
Desc: Enhance existing rateLimiter.ts (currently 60 req/60s per IP). Add per-user rate limiting keyed by wallet address (30 req/60s). Add separate limit for prepare-* endpoints (10 req/10s) to prevent burst traffic. Reference dca-service pattern: tiered limits by endpoint type. Files: backend/src/middleware/rateLimiter.ts.