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/projects.json

@@ -4,16 +4,26 @@
   "editProject": "Edit Project",
   "deleteProject": "Delete Project",
   "projectSettings": "Project Settings",
+  "newProject": "New Project",
   "fields": {
     "name": "Name",
     "namePlaceholder": "Enter project name",
+    "title": "Project Title",
+    "titlePlaceholder": "Enter project title",
     "description": "Description",
-    "descriptionPlaceholder": "Enter project description",
+    "descriptionPlaceholder": "Description (optional)",
     "status": "Status",
     "startDate": "Start Date",
     "endDate": "End Date",
     "owner": "Project Owner",
-    "space": "Space"
+    "space": "Space",
+    "securityLevel": "Security Level"
+  },
+  "securityLevel": {
+    "label": "Security Level",
+    "public": "Public - All users",
+    "department": "Department - Same department only",
+    "confidential": "Confidential - Owner only"
   },
   "status": {
     "planning": "Planning",
@@ -37,10 +47,18 @@
     "overdue": "Overdue",
     "progress": "Overall Progress"
   },
+  "card": {
+    "tasks": "{{count}} tasks",
+    "owner": "Owner",
+    "noDescription": "No description",
+    "unknown": "Unknown"
+  },
   "messages": {
-    "created": "Project created",
+    "created": "Project created successfully",
     "updated": "Project updated",
     "deleted": "Project deleted",
+    "loadFailed": "Failed to load projects",
+    "createFailed": "Failed to create project",
     "confirmDelete": "Are you sure you want to delete this project? This will delete all related tasks."
   },
   "empty": {