- Lazy Sentry profiling: defer @sentry/profiling-node native addon load
  until after server.listen() via setImmediate, saving ~30-50ms on cold start
- Deferred background services: jobs, BullMQ scheduler, queue processors,
  webhook worker, batch processor, and Redis connection all start after the
  server is already accepting requests (inside listen() callback)
- Lazy sandbox initialization: SandboxManager, MockPaymentProcessor, and
  TestDataSeeder constructed on first use via getter functions, not at module scope
- Fixed import ordering: all imports moved to top of file (ESM requirement),
  removed mid-file import that was between route registrations
- Added missing gdprRouter import that caused a ReferenceError at runtime
- Removed dead imports: SecurityMiddleware, SecurityMonitor, sanitizeInput,
  contentSecurityPolicy, rateLimitAnalyticsRouter, sessionsRouter, stripeRouter,
  signaturesRouter were imported but never used

workers/src/index.ts:
- Code splitting via classifyRoute() + getHandler() with handler cache
  for execution context reuse across requests in the same isolate
- Cold start detection: isFirstRequest flag captures init duration on first
  request and persists to KV for the monitoring dashboard
- Warm-up scheduling: scheduled() export handles Cloudflare cron trigger,
  proxies to backend /api/v1/cold-start/warmup every 5 minutes
- Warmup proxies to backend so backend lastRequestAt is updated correctly

workers/wrangler.toml:
- Added cron trigger every 5 minutes for warm-up scheduling

backend/src/lib/lazy-loader.ts (new):
- lazyLoad(), lazySyncLoad(), trackedLazyLoad() utilities for deferred
  module initialization with a registry for the monitoring dashboard

backend/src/middleware/cold-start.ts (new):
- Per-request cold start tracking middleware with p50/p95/p99 latency
- Detects first-request and idle-gap cold starts, records init duration
- Fixed idle-gap initDurationMs to report actual gap duration

backend/src/routes/cold-start-monitor.ts (new):
- GET  /api/v1/cold-start/metrics  - full snapshot, p95 target compliance
- GET  /api/v1/cold-start/summary  - lightweight dashboard summary
- POST /api/v1/cold-start/reset    - reset counters
- POST /api/v1/cold-start/warmup   - warm-up ping endpoint for schedulers