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/settings.json

@@ -2,6 +2,21 @@
   "title": "設定",
   "projectSettings": "專案設定",
   "backToTasks": "返回任務",
+  "mySettings": {
+    "title": "個人設定",
+    "profile": "個人資訊",
+    "email": "電子郵件",
+    "department": "部門",
+    "role": "角色",
+    "workloadSettings": "工作負載設定",
+    "capacityDescription": "設定您每週可用的工作時數，用於計算工作負載百分比。",
+    "weeklyCapacity": "每週容量",
+    "hoursPerWeek": "小時/週",
+    "capacityHelp": "建議值：40 小時（標準工時）。最大值：168 小時（一週總時數）。",
+    "capacitySaved": "容量設定已儲存",
+    "capacityError": "儲存容量設定失敗",
+    "capacityInvalid": "請輸入有效的時數（0-168）"
+  },
   "tabs": {
     "general": "一般",
     "members": "成員",
@@ -37,16 +52,58 @@
     "add": "新增欄位",
     "edit": "編輯欄位",
     "delete": "刪除欄位",
+    "create": "建立欄位",
     "fieldName": "欄位名稱",
+    "fieldNamePlaceholder": "例如：故事點數、衝刺編號",
     "fieldType": "欄位類型",
     "required": "必填",
+    "requiredField": "必填欄位",
+    "requiredHelp": "建立或更新任務時必須填寫必填欄位。",
+    "cannotChangeType": "無法變更",
+    "description": "自訂欄位允許您為任務新增額外資料。每個專案最多可建立 20 個欄位。",
+    "loading": "載入自訂欄位中...",
+    "loadError": "載入自訂欄位失敗",
+    "retry": "重試",
+    "empty": "尚未定義任何自訂欄位。",
+    "emptyHint": "點擊「新增欄位」建立您的第一個自訂欄位。",
+    "deleteConfirmTitle": "刪除自訂欄位？",
+    "deleteConfirmMessage": "這將永久刪除此欄位及所有任務中儲存的值。此操作無法復原。",
+    "deleting": "刪除中...",
+    "deleted": "自訂欄位已刪除",
+    "deleteError": "刪除欄位失敗",
+    "saving": "儲存中...",
+    "saveChanges": "儲存變更",
+    "saveError": "儲存欄位失敗",
+    "options": "選項",
+    "optionPlaceholder": "選項 {{index}}",
+    "addOption": "新增選項",
+    "optionRequired": "下拉欄位至少需要一個選項",
+    "formula": "公式運算式",
+    "formulaPlaceholder": "例如：{time_spent} / {original_estimate} * 100",
+    "formulaRequired": "公式運算式為必填",
+    "formulaHelp": {
+      "intro": "使用大括號來參照其他欄位：",
+      "customField": "參照自訂數字欄位",
+      "estimate": "任務預估時間",
+      "timeSpent": "已記錄時間",
+      "operators": "支援的運算子：+, -, *, /"
+    },
     "types": {
       "text": "文字",
+      "textDesc": "單行文字輸入",
       "number": "數字",
+      "numberDesc": "數值",
       "date": "日期",
-      "select": "下拉選單",
-      "multiSelect": "多選",
-      "checkbox": "核取方塊"
+      "dateDesc": "日期選擇器",
+      "dropdown": "下拉選單",
+      "dropdownDesc": "從預設選項中選擇",
+      "person": "人員",
+      "personDesc": "使用者指派",
+      "formula": "公式",
+      "formulaDesc": "從其他欄位計算"
+    },
+    "validation": {
+      "nameRequired": "欄位名稱為必填"
     }
   },
   "notifications": {