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/commands/test-coverage.md

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+# Test Coverage
+
+Analyze test coverage and generate missing tests:
+
+1. Run tests with coverage: npm test --coverage or pnpm test --coverage
+
+2. Analyze coverage report (coverage/coverage-summary.json)
+
+3. Identify files below 80% coverage threshold
+
+4. For each under-covered file:
+   - Analyze untested code paths
+   - Generate unit tests for functions
+   - Generate integration tests for APIs
+   - Generate E2E tests for critical flows
+
+5. Verify new tests pass
+
+6. Show before/after coverage metrics
+
+7. Ensure project reaches 80%+ overall coverage
+
+Focus on:
+- Happy path scenarios
+- Error handling
+- Edge cases (null, undefined, empty)
+- Boundary conditions