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/en/settings.json

@@ -1,6 +1,7 @@
 {
   "title": "Settings",
   "projectSettings": "Project Settings",
+  "backToTasks": "Back to Tasks",
   "tabs": {
     "general": "General",
     "members": "Members",
@@ -13,10 +14,13 @@
     "title": "General Settings",
     "projectName": "Project Name",
     "description": "Description",
+    "noDescription": "No description",
+    "securityLevel": "Security Level",
     "status": "Status",
     "visibility": "Visibility",
     "public": "Public",
-    "private": "Private"
+    "private": "Private",
+    "helpText": "To edit project details, contact the project owner."
   },
   "members": {
     "title": "Member Management",