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>

frontend/public/locales/zh-TW/workload.json

@@ -30,13 +30,43 @@
     "overloaded": "超載",
     "underutilized": "低使用率"
   },
+  "table": {
+    "member": "團隊成員",
+    "department": "部門",
+    "allocated": "已分配",
+    "capacity": "容量",
+    "load": "負載",
+    "status": "狀態"
+  },
   "status": {
     "balanced": "平衡",
+    "normal": "正常",
+    "warning": "警告",
     "overloaded": "超載",
+    "unavailable": "無法使用",
     "underutilized": "低使用率"
   },
   "empty": {
     "title": "沒有工作負載資料",
-    "description": "目前沒有足夠的資料來顯示工作負載"
+    "description": "目前沒有足夠的資料來顯示工作負載",
+    "noTasks": "本週沒有任何人被指派任務",
+    "hint": "當團隊成員被指派任務且截止日期在本週時，他們將會顯示在這裡。"
+  },
+  "options": {
+    "showAllUsers": "顯示所有用戶",
+    "showAllUsersHint": "（包括沒有任務的用戶）"
+  },
+  "calculation": {
+    "title": "工作負載計算方式",
+    "formula": "工作負載 = 本週任務預估工時 ÷ 個人週容量 × 100%",
+    "requirements": "任務需符合以下條件才會計入：",
+    "req1": "任務已指派給該成員",
+    "req2": "任務截止日期在選擇的週內",
+    "req3": "任務設有預估工時（original_estimate）",
+    "req4": "任務尚未完成",
+    "thresholds": "負載等級閾值：",
+    "normal": "正常：< 80%",
+    "warning": "警告：80% - 99%",
+    "overloaded": "超載：≥ 100%"
   }
 }