Add new skills for backend patterns, coding standards, continuous learning, and NestJS best practices

- Introduced backend patterns skill with guidelines on API design, database optimization, and server-side best practices.
- Added coding standards skill outlining universal coding principles for TypeScript, NestJS, and Node.js development.
- Implemented continuous learning skill to automatically extract reusable patterns from Cursor sessions.
- Created NestJS best practices skill detailing architecture patterns, dependency injection, error handling, and security measures.
- Included various rules and templates for NestJS best practices to ensure production-ready applications.

.cursor/rules/testing.mdc

@@ -0,0 +1,36 @@
+---
+description: TDD workflow, 80% coverage minimum, and NestJS unit/e2e requirements
+alwaysApply: true
+---
+
+# Testing Requirements
+
+## Minimum Test Coverage: 80%
+
+Test Types (ALL required):
+1. **Unit Tests** - Services, guards, pipes, utilities (`*.spec.ts`)
+2. **Integration Tests** - NestJS testing module + Drizzle
+3. **E2E Tests** - HTTP flows with Supertest (`test/*.e2e-spec.ts`)
+
+## Test-Driven Development
+
+MANDATORY workflow:
+1. Write test first (RED)
+2. Run test - it should FAIL
+3. Write minimal implementation (GREEN)
+4. Run test - it should PASS
+5. Refactor (IMPROVE)
+6. Verify coverage (80%+)
+
+## Troubleshooting Test Failures
+
+1. Use **tdd-guide** agent
+2. Check test isolation
+3. Verify mocks are correct
+4. Fix implementation, not tests (unless tests are wrong)
+
+## Agent Support
+
+- **tdd-guide** - Use PROACTIVELY for new features, enforces write-tests-first
+- **e2e-runner** - NestJS E2E (Supertest) specialist
+- Skill: `.agents/skills/tdd-workflow/`