feat: complete i18n translation for remaining components

- Translate pages: Projects, ProjectHealthPage, ProjectSettings
- Translate components: TaskDetailModal, KanbanBoard, Comments,
  SubtaskList, CalendarView, BlockerDialog
- Add translation keys for tasks namespace: kanban, calendar,
  subtasks.error, comments.error, blockers (full translation)
- Add common.labels.task translation key
- Fix task creation: use original_estimate instead of time_estimate

Translation coverage:
- 10 locale files updated (zh-TW & en)
- 6 page/component files translated
- ~100 new translation keys added

🤖 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

@@ -1,6 +1,7 @@
 {
   "title": "設定",
   "projectSettings": "專案設定",
+  "backToTasks": "返回任務",
   "tabs": {
     "general": "一般",
     "members": "成員",
@@ -13,10 +14,13 @@
     "title": "一般設定",
     "projectName": "專案名稱",
     "description": "描述",
+    "noDescription": "沒有描述",
+    "securityLevel": "安全等級",
     "status": "狀態",
     "visibility": "可見性",
     "public": "公開",
-    "private": "私人"
+    "private": "私人",
+    "helpText": "如需編輯專案詳情，請聯繫專案負責人。"
   },
   "members": {
     "title": "成員管理",