feat: implement soft delete, task editing fixes, and UI improvements

Backend:
- Add soft delete for spaces and projects (is_active flag)
- Add status_id and assignee_id to TaskUpdate schema
- Fix task PATCH endpoint to update status and assignee
- Add validation for assignee_id and status_id in task updates
- Fix health service to count tasks with "Blocked" status as blockers
- Filter out deleted spaces/projects from health dashboard
- Add workload cache invalidation on assignee changes

Frontend:
- Add delete confirmation dialogs for spaces and projects
- Fix UserSelect to display selected user name (valueName prop)
- Fix task detail modal to refresh data after save
- Enforce 2-level subtask depth limit in UI
- Fix timezone bug in date formatting (use local timezone)
- Convert NotificationBell from Tailwind to inline styles
- Add i18n translations for health, workload, settings pages
- Add parent_task_id to Task interface across components

OpenSpec:
- Archive add-delete-capability change

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/app/api/projects/router.py

@@ -52,7 +52,7 @@ async def list_projects_in_space(
             detail="Access denied",
         )
 
-    projects = db.query(Project).filter(Project.space_id == space_id).all()
+    projects = db.query(Project).filter(Project.space_id == space_id, Project.is_active == True).all()
 
     # Filter by project access
     accessible_projects = [p for p in projects if check_project_access(current_user, p)]
@@ -154,7 +154,7 @@ async def get_project(
     """
     Get a project by ID.
     """
-    project = db.query(Project).filter(Project.id == project_id).first()
+    project = db.query(Project).filter(Project.id == project_id, Project.is_active == True).first()
 
     if not project:
         raise HTTPException(
@@ -202,7 +202,7 @@ async def update_project(
     """
     Update a project.
     """
-    project = db.query(Project).filter(Project.id == project_id).first()
+    project = db.query(Project).filter(Project.id == project_id, Project.is_active == True).first()
 
     if not project:
         raise HTTPException(
@@ -317,7 +317,7 @@ async def list_project_statuses(
     """
     List all task statuses for a project.
     """
-    project = db.query(Project).filter(Project.id == project_id).first()
+    project = db.query(Project).filter(Project.id == project_id, Project.is_active == True).first()
 
     if not project:
         raise HTTPException(