feat: add health check page (#244)

frontend/messages/en.json

@@ -114,6 +114,14 @@
     "not_own_any_projects": "You don't own any projects.",
     "find_projects": "Find projects"
   },
+  "Health": {
+    "health_check": "Health Check",
+    "status": "Status",
+    "ok": "OK",
+    "error": "Error",
+    "api_server": "API Server",
+    "unittcms_version": "UnitTCMS Version"
+  },
   "Admin": {
     "user_management": "User Management",
     "avatar": "Avatar",

frontend/messages/ja.json

@@ -133,6 +133,14 @@
     "lost_admin_auth": "管理者権限を失いました",
     "at_least": "最低1人以上の管理者が必要です。"
   },
+  "Health": {
+    "health_check": "ヘルスチェック",
+    "status": "ステータス",
+    "ok": "正常",
+    "error": "エラー",
+    "api_server": "APIサーバー",
+    "unittcms_version": "UnitTCMS バージョン"
+  },
   "Projects": {
     "project_list": "プロジェクト一覧",
     "new_project": "新規プロジェクト",