Closes three CSRF security gaps identified in code review:
1. Added X-CSRF-Token and X-Workspace-Id to CORS allowed headers
- Updated apps/api/src/main.ts to accept CSRF token headers
2. Integrated CSRF token handling in web client
- Added fetchCsrfToken() to fetch token from API
- Store token in memory (not localStorage for security)
- Automatically include X-CSRF-Token in POST/PUT/PATCH/DELETE
- Implement automatic token refresh on 403 CSRF errors
- Added comprehensive test coverage for CSRF functionality
3. Applied CSRF Guard globally
- Added CsrfGuard as APP_GUARD in app.module.ts
- Verified @SkipCsrf() decorator works for exempted endpoints
All tests passing. CSRF protection now enforced application-wide.
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>