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/schemas/project_health.py

@@ -54,9 +54,10 @@ class ProjectHealthWithDetails(ProjectHealthResponse):
 class ProjectHealthSummary(BaseModel):
     """Aggregated health metrics across all projects."""
     total_projects: int
-    healthy_count: int  # health_score >= 80
-    at_risk_count: int  # health_score 50-79
-    critical_count: int  # health_score < 50
+    healthy_count: int  # health_score >= 80 (low risk)
+    at_risk_count: int  # health_score 60-79 (medium risk)
+    high_risk_count: int  # health_score 40-59 (high risk)
+    critical_count: int  # health_score < 40 (critical risk)
     average_health_score: float
     projects_with_blockers: int
     projects_delayed: int