feat: implement security, error resilience, and query optimization proposals

Security Validation (enhance-security-validation):
- JWT secret validation with entropy checking and pattern detection
- CSRF protection middleware with token generation/validation
- Frontend CSRF token auto-injection for DELETE/PUT/PATCH requests
- MIME type validation with magic bytes detection for file uploads

Error Resilience (add-error-resilience):
- React ErrorBoundary component with fallback UI and retry functionality
- ErrorBoundaryWithI18n wrapper for internationalization support
- Page-level and section-level error boundaries in App.tsx

Query Performance (optimize-query-performance):
- Query monitoring utility with threshold warnings
- N+1 query fixes using joinedload/selectinload
- Optimized project members, tasks, and subtasks endpoints

Bug Fixes:
- WebSocket session management (P0): Return primitives instead of ORM objects
- LIKE query injection (P1): Escape special characters in search queries

Tests: 543 backend tests, 56 frontend tests passing

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

openspec/changes/archive/2026-01-11-optimize-query-performance/proposal.md

@@ -0,0 +1,19 @@
+# Change: Optimize Database Query Performance
+
+## Why
+
+QA review identified N+1 query patterns in project member listing and related endpoints. When loading a project with many members, each member triggers a separate database query, causing significant performance degradation.
+
+## What Changes
+
+- Implement eager loading (joinedload) for project member relationships
+- Add query batching for related entity loading
+- Add database query logging in development mode for detection
+
+## Impact
+
+- Affected specs: `resource-management`
+- Affected code:
+  - `backend/app/services/project_service.py` - Member loading
+  - `backend/app/api/v1/endpoints/projects.py` - Query optimization
+  - `backend/app/models/` - Relationship configurations