✅ test: implement comprehensive automated testing system with daily CI/CD

Implement rock-solid automated testing infrastructure for mana-core-auth
with daily execution, notifications, and comprehensive monitoring.

Test Suite Improvements:
- Fix all 36 failing BetterAuthService tests (missing service mocks)
- Add 21 JwtAuthGuard tests achieving 100% statement coverage
- Create silentError helper to suppress intentional error logs
- Fix Todo backend TaskService test structure
- Add jose mock for JWT testing
- Configure jest collectCoverageFrom for mana-core-auth

GitHub Actions Workflow:
- Daily automated test execution (2 AM UTC + manual trigger)
- Matrix parallelization across 6 backend services
- PostgreSQL and Redis service containers
- Coverage enforcement (80% threshold)
- Multi-channel notifications (Discord, Slack, GitHub Issues)
- Support for success notifications (opt-in)

Test Infrastructure:
- Coverage aggregation across multiple services
- Flaky test detection with 30-run history tracking
- Performance metrics tracking with regression detection
- Test data seeding and cleanup scripts
- Comprehensive test reporting with formatted metrics

Documentation:
- TESTING_GUIDE.md (4000+ words) - Complete testing documentation
- AUTOMATED_TESTING_SYSTEM.md - System architecture and workflows
- DISCORD_NOTIFICATIONS_SETUP.md - Discord webhook setup guide
- TESTING_DEPLOYMENT_CHECKLIST.md - Pre-deployment verification
- TESTING_QUICK_REFERENCE.md - Quick command reference

Final Result:
- 180/180 tests passing (100% pass rate)
- Zero console errors in test output
- Automated daily testing with rich notifications
- Production-ready test infrastructure

docs/README.md

@@ -18,6 +18,7 @@ Welcome to the Manacore monorepo documentation. This guide helps you find exactl
 | **Configure CI/CD** | [CI/CD Setup](CI_CD_SETUP.md) |
 | **Work with runtime config** | [Runtime Config](RUNTIME_CONFIG.md) |
 | **Self-host the platform** | [Self-Hosting Guide](SELF-HOSTING-GUIDE.md) |
+| **Run and write tests** | [Testing Guide](TESTING_GUIDE.md) |
 
 ## 📁 Documentation Structure
 
@@ -53,7 +54,8 @@ CI/CD, staging, production deployment, and operational procedures.
 - [I18N](I18N.md) - Internationalization
 - [User Settings](USER_SETTINGS.md) - User settings architecture
 - [Self-Hosting Guide](SELF-HOSTING-GUIDE.md) - Self-hosting instructions
-- [Testing Guide](TESTING.md) - Testing strategies
+- [Testing Guide](TESTING_GUIDE.md) - Comprehensive testing documentation
+- [Testing Quick Reference](TESTING_QUICK_REFERENCE.md) - Common testing commands and patterns
 
 ### Project-Specific
 - [ManaDeck Postgres Migration](MANADECK_POSTGRES_MIGRATION.md) - ManaDeck database migration
@@ -89,4 +91,4 @@ When updating documentation:
 
 ---
 
-**Last Updated:** 2025-12-16
+**Last Updated:** 2025-12-25