feat(shared,tests): add error boundaries, lib utils, i18n messages, and integration tests

shared:

- Add class-filter, error-state, route-error, section-error-boundary, widget-boundary components

- Add ui/alert component

- Add constants directory

- Add breached-password, export-utils, permission-bitmap, rate-limit, resolve-action-error, route-permissions, route-resolver, type-guards lib

- Add i18n messages (en, zh-CN) for invitation-codes, parent, questions, rbac

tests:

- Add integration tests for elective

- Add tests/setup/empty-stub

scripts:

- Add update-md.cjs, tmp_append_en.ps1, tmp_merge_en.ps1 utilities

src/shared/i18n/messages/en/leave.json

@@ -1,6 +1,12 @@
 {
   "title": "Leave Request",
+  "title.parent": "Online Leave",
+  "title.teacher": "Leave Approval",
+  "title.student": "My Leave Requests",
   "description": "Submit a leave request for your child.",
+  "description.parent": "Submit a leave request for your child. Attendance is auto-synced after homeroom teacher approval.",
+  "description.teacher": "View and approve leave requests from students in your classes. Approved leaves automatically mark attendance as 'excused'.",
+  "description.student": "Submit your own leave request. It takes effect after homeroom teacher approval.",
   "backToDashboard": "Back to Dashboard",
   "onlineLeave": "Online Leave Request",
   "comingSoon": "Coming soon",
@@ -8,5 +14,68 @@
   "contactOptions": "Contact options",
   "callOffice": "Call the school office during working hours",
   "sendMessage": "Send a message to the homeroom teacher via the Messages page",
-  "goToMessages": "Go to Messages"
-}
+  "goToMessages": "Go to Messages",
+  "types": {
+    "sick": "Sick Leave",
+    "personal": "Personal Leave",
+    "family": "Family Affairs",
+    "other": "Other"
+  },
+  "status": {
+    "pending": "Pending",
+    "approved": "Approved",
+    "rejected": "Rejected",
+    "cancelled": "Cancelled"
+  },
+  "form": {
+    "student": "Student",
+    "studentPlaceholder": "Select your child",
+    "leaveType": "Leave Type",
+    "dateRange": "Leave Dates",
+    "reason": "Reason",
+    "reasonPlaceholder": "Briefly explain the reason for leave (max 500 chars)",
+    "submit": "Submit Request",
+    "submitting": "Submitting…"
+  },
+  "list": {
+    "reason": "Reason",
+    "reviewedBy": "Reviewed by {name} ({date})",
+    "reviewComment": "Review Comment",
+    "attendanceSynced": "Attendance synced"
+  },
+  "review": {
+    "title": "Review Leave Request",
+    "description": "{name} · {className} · {dateRange}",
+    "approve": "Approve",
+    "reject": "Reject",
+    "cancel": "Cancel",
+    "commentLabel": "Review Comment",
+    "commentPlaceholder": "Enter review comment (required for rejection, optional for approval)",
+    "openButton": "Review"
+  },
+  "errors": {
+    "invalidForm": "The form has errors, please check and retry",
+    "noRelation": "You have no parent-child relation with this student",
+    "classMismatch": "Selected class does not match the student's current class",
+    "overlappingLeave": "An active leave request already exists in this date range",
+    "reviewCommentRequired": "Review comment is required when rejecting",
+    "notFound": "Leave request not found or no access",
+    "alreadyReviewed": "This leave request has already been reviewed",
+    "notOwner": "You can only cancel your own leave requests",
+    "cannotCancel": "Current status does not allow cancellation (only pending can be cancelled)"
+  },
+  "messages": {
+    "created": "Leave request submitted, waiting for homeroom teacher approval",
+    "approved": "Leave request approved, attendance synced",
+    "rejected": "Leave request rejected",
+    "cancelled": "Leave request cancelled"
+  },
+  "empty": {
+    "parentTitle": "No leave records",
+    "parentDesc": "You have not submitted any leave requests for your children",
+    "teacherTitle": "No leave requests",
+    "teacherDesc": "No pending or reviewed leave requests from your classes",
+    "studentTitle": "No leave records",
+    "studentDesc": "You have not submitted any leave requests"
+  }
+}