feat: implement 5 QA-driven security and quality proposals

Implemented proposals from comprehensive QA review:

1. extend-csrf-protection
   - Add POST to CSRF protected methods in frontend
   - Global CSRF middleware for all state-changing operations
   - Update tests with CSRF token fixtures

2. tighten-cors-websocket-security
   - Replace wildcard CORS with explicit method/header lists
   - Disable query parameter auth in production (code 4002)
   - Add per-user WebSocket connection limit (max 5, code 4005)

3. shorten-jwt-expiry
   - Reduce JWT expiry from 7 days to 60 minutes
   - Add refresh token support with 7-day expiry
   - Implement token rotation on refresh
   - Frontend auto-refresh when token near expiry (<5 min)

4. fix-frontend-quality
   - Add React.lazy() code splitting for all pages
   - Fix useCallback dependency arrays (Dashboard, Comments)
   - Add localStorage data validation in AuthContext
   - Complete i18n for AttachmentUpload component

5. enhance-backend-validation
   - Add SecurityAuditMiddleware for access denied logging
   - Add ErrorSanitizerMiddleware for production error messages
   - Protect /health/detailed with admin authentication
   - Add input length validation (comment 5000, desc 10000)

All 521 backend tests passing. Frontend builds successfully.

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

backend/app/schemas/project_template.py

@@ -25,7 +25,7 @@ class CustomFieldDefinition(BaseModel):
 class ProjectTemplateBase(BaseModel):
     """Base schema for project template."""
     name: str = Field(..., min_length=1, max_length=200)
-    description: Optional[str] = None
+    description: Optional[str] = Field(None, max_length=2000)
     is_public: bool = Field(default=False)
     task_statuses: Optional[List[TaskStatusDefinition]] = None
     custom_fields: Optional[List[CustomFieldDefinition]] = None
@@ -43,7 +43,7 @@ class ProjectTemplateCreate(ProjectTemplateBase):
 class ProjectTemplateUpdate(BaseModel):
     """Schema for updating a project template."""
     name: Optional[str] = Field(None, min_length=1, max_length=200)
-    description: Optional[str] = None
+    description: Optional[str] = Field(None, max_length=2000)
     is_public: Optional[bool] = None
     task_statuses: Optional[List[TaskStatusDefinition]] = None
     custom_fields: Optional[List[CustomFieldDefinition]] = None