feat: add relay notification and comprehensive E2E tests
- Add notifyCrawlers() to notify relays after writes via requestCrawl
- Add worker-level routing for sync endpoints (getLatestCommit, getRepoStatus, getRepo, getRecord)
- Fix /init to register handles in default DO's handleMap
- Add self-contained E2E test suite (23 tests) covering:
- Server basics, identity, authentication
- Repo CRUD, applyWrites batch operations
- Sync endpoints (CAR file retrieval)
- Error handling (401, 403, 404)
- Move test credentials to .dev.vars (gitignored)
- Update .env.example with all config options
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>