feat(portal-shell): grades 模块 5 页迁移（教师域 §9.1 B2）

§9.1 B2 grades 行：/grades、/entry、/analytics、/stats、/report-card
契约：grade(id) ✅ 真实查询；列表/分析/统计/成绩单 → MSW 兜底

新增文件：
- src/lib/api/grades.ts (6 hooks)
- src/lib/api/operations/grades.graphql.ts (6 documents)
- src/features/teacher/grades/ (7 files: transformations + tests + 5 clients)
- src/app/shell/teacher/grades/ (5 page.tsx + loading.tsx + error.tsx)

修改文件：
- src/mocks/graphql-data.ts (5 mock 常量 + 6 handler cases)
- src/messages/{zh-CN,en}.json (grades i18n)
- src/lib/api/{index,operations/index}.ts (导出 grades)
- scripts/check-page-count.ts (baseline 26 → 31)

DoD 验收（§11.3 11 项）：
- typecheck 0 errors
- lint 0 errors
- vitest 357 tests passed
- lint:tokens 0 errors
- check:pages 31 PASS

关联：ARCHITECTURE.md §5.3 / §5.4 / §9.1 / §10 P2 / §11.3 / §11.4

apps/portal-shell/src/messages/en.json

@@ -513,7 +513,125 @@
     }
   },
   "grades": {
-    "title": "Grades"
+    "title": "Grades",
+    "list": {
+      "title": "Grades",
+      "description": "View and manage all student grades",
+      "entry": "Record Grade",
+      "searchPlaceholder": "Search by student name/no...",
+      "statusFilter": "Filter by status",
+      "statusAll": "All statuses",
+      "statusGraded": "Graded",
+      "statusPending": "Pending",
+      "statusExempt": "Exempt",
+      "statusAbsent": "Absent",
+      "total": "{count} total",
+      "colStudent": "Student",
+      "colClass": "Class",
+      "colSource": "Source",
+      "colScore": "Score",
+      "colStatus": "Status",
+      "colGradedAt": "Graded At",
+      "mswNotice": "List query contract is pending, please ensure NEXT_PUBLIC_MSW=1 is enabled."
+    },
+    "entry": {
+      "title": "Record Grade",
+      "description": "Fill in student grade information",
+      "submit": "Submit",
+      "success": "Grade recorded successfully",
+      "error": "Submission failed",
+      "classId": "Class ID",
+      "studentId": "Student ID",
+      "examId": "Exam ID (optional)",
+      "examIdPlaceholder": "e.g. exam-001",
+      "homeworkId": "Homework ID (optional)",
+      "homeworkIdPlaceholder": "e.g. hw-001",
+      "score": "Score",
+      "totalScore": "Total Score",
+      "feedbackLabel": "Feedback",
+      "feedbackPlaceholder": "Write feedback to the student...",
+      "errorClassRequired": "Please fill in Class ID",
+      "errorStudentRequired": "Please fill in Student ID",
+      "errorScoreInvalid": "Score is invalid, please enter a non-negative number",
+      "errorTotalInvalid": "Total score is invalid, please enter a positive number",
+      "errorSourceRequired": "At least one of Exam ID or Homework ID is required",
+      "contractPending": "Grade submission contract is @contract-pending, currently backed by MSW. Will switch to real submission once backend mutation is ready."
+    },
+    "analytics": {
+      "title": "Grade Analytics",
+      "subtitle": "Scope: {scope}",
+      "notFound": "No analytics data found, grading may not be complete",
+      "sectionSummary": "Summary",
+      "sectionDistribution": "Score Distribution",
+      "sectionRankings": "Student Rankings",
+      "summaryTotal": "Expected",
+      "summaryGraded": "Graded",
+      "summaryAvg": "Average",
+      "summaryMax": "Max",
+      "summaryMin": "Min",
+      "summaryPassRate": "Pass Rate",
+      "summaryPassScore": "Pass Score",
+      "emptyDistribution": "No score distribution data",
+      "emptyRankings": "No ranking data",
+      "colRank": "Rank",
+      "colStudentNo": "Student No.",
+      "colStudentName": "Name",
+      "colScore": "Score",
+      "colLevel": "Level"
+    },
+    "stats": {
+      "title": "Grade Statistics",
+      "subtitle": "Class: {classId} · Period: {period}",
+      "notFound": "No statistics data found",
+      "empty": "No subject statistics data",
+      "sectionSummary": "Subject Summary Cards",
+      "sectionTable": "Subject Statistics Table",
+      "studentCount": "{count} students",
+      "avgScore": "Average",
+      "maxScore": "Max",
+      "minScore": "Min",
+      "passRate": "Pass Rate",
+      "passCount": "Pass Count",
+      "failCount": "Fail Count",
+      "colSubject": "Subject",
+      "colClass": "Class",
+      "colStudentCount": "Students",
+      "colAvgScore": "Average",
+      "colMaxScore": "Max",
+      "colMinScore": "Min",
+      "colPassRate": "Pass Rate",
+      "colPassCount": "Pass Count",
+      "colFailCount": "Fail Count"
+    },
+    "reportCard": {
+      "title": "Report Card",
+      "titleWithName": "{name}'s Report Card",
+      "subtitle": "No.: {no} · Class: {className} · Period: {period}",
+      "notFound": "No report card data found",
+      "sectionBasic": "Student Info",
+      "sectionEntries": "Subject Grades",
+      "sectionSummary": "Summary",
+      "fieldStudentName": "Name",
+      "fieldStudentNo": "Student No.",
+      "fieldClass": "Class",
+      "fieldPeriod": "Period",
+      "colSubject": "Subject",
+      "colSource": "Source",
+      "colScore": "Score",
+      "colLevel": "Level",
+      "colFeedback": "Feedback",
+      "colGradedAt": "Graded At",
+      "emptyEntries": "No subject grades",
+      "totalAvgScore": "Total Average",
+      "totalRank": "Total Rank",
+      "totalStudents": "Total Students",
+      "rankValue": "Rank {rank} / {total}"
+    },
+    "error": {
+      "title": "Grades page error",
+      "unknown": "Unknown error",
+      "retry": "Retry"
+    }
   },
   "analytics": {
     "title": "Analytics"