feat(textbooks): 知识图谱功能全面重构 — 前置依赖 + dagre 布局 + React Flow 可视化 + 师生双视角

将教材模块图谱从基本无用状态升级为完整知识图谱可视化系统。

数据层：新增 knowledgePointPrerequisites 表（复合主键+双外键 cascade）；新增 data-access-graph.ts（server-only）知识点关联聚合、学生/班级掌握度查询；utils.ts 新增 hasCycleAfterAddingEdge（DFS 循环依赖检测）。

业务层：3 个新 Server Action（getKnowledgeGraphDataAction 三视图模式、createPrerequisiteAction 含循环检测、deletePrerequisiteAction）；graph-layout.ts 重写为 dagre 分层有向图布局。

视图层：knowledge-graph.tsx 重写为 React Flow 主组件（全书视图+搜索高亮+关联节点高亮+章节着色）；4 个新组件（graph-kp-node/graph-prerequisite-edge/graph-toolbar/graph-node-detail-panel）；use-graph-data.ts 派生值模式避免 effect 中 setState。

架构：严格三层架构，客户端通过 Server Action 间接访问 server-only 数据层；权限校验+ i18n 全覆盖；架构文档 004/005 同步。

测试：utils.test.ts 新增 5 个循环检测测试，graph-layout.test.ts 重写 5 个 dagre 布局测试，全部 30 个教材模块单元测试通过。

附带提交 drizzle/0005 error-book 迁移文件以保持 journal 一致性。

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

@@ -34,10 +34,16 @@
       "graph": "Graph"
     },
     "selectChapter": "Please select a chapter to start reading.",
+    "selectChapterDesc": "Choose a chapter from the sidebar to view its content.",
     "selectChapterKnowledge": "Please select a chapter to view knowledge points.",
+    "selectChapterKnowledgeDesc": "Choose a chapter from the sidebar to see its knowledge points.",
     "selectChapterGraph": "Please select a chapter to view the knowledge graph.",
+    "selectChapterGraphDesc": "Choose a chapter from the sidebar to see its knowledge graph.",
     "emptyKnowledge": "No knowledge points in this chapter yet.",
+    "emptyKnowledgeDesc": "Select text while reading to create a knowledge point.",
     "emptyContent": "No content yet",
+    "emptyContentDesc": "Click \"Edit Content\" to start writing this chapter.",
+    "loadingKnowledge": "Loading knowledge points...",
     "editContent": "Edit Content",
     "cancel": "Cancel",
     "save": "Save",
@@ -45,7 +51,9 @@
     "addKnowledgePoint": "Add Knowledge Point",
     "clickToViewKp": "Click to view knowledge point details",
     "noChapters": "No chapters",
-    "noChaptersDesc": "This textbook has no chapters yet."
+    "noChaptersDesc": "This textbook has no chapters yet.",
+    "sidebar": "Chapters & Knowledge",
+    "openSidebar": "Open Sidebar"
   },
   "dialog": {
     "create": {
@@ -75,7 +83,11 @@
       "deleting": "Deleting...",
       "cannotDeleteWithSubchapters": "Cannot delete chapter with subchapters",
       "addSubchapter": "Add Subchapter",
-      "titlePlaceholder": "e.g. Chapter 1: Introduction"
+      "titlePlaceholder": "e.g. Chapter 1: Introduction",
+      "toggle": "Toggle",
+      "orderUpdated": "Order updated",
+      "cancel": "Cancel",
+      "dragHandle": "Drag to reorder"
     },
     "knowledge": {
       "createTitle": "Add Knowledge Point",
@@ -133,6 +145,7 @@
     "level": "Lv."
   },
   "subject": {
+    "chinese": "Chinese",
     "mathematics": "Mathematics",
     "physics": "Physics",
     "chemistry": "Chemistry",
@@ -142,6 +155,8 @@
     "geography": "Geography"
   },
   "grade": {
+    "grade1": "Grade 1",
+    "grade2": "Grade 2",
     "grade7": "Grade 7",
     "grade8": "Grade 8",
     "grade9": "Grade 9",
@@ -160,7 +175,7 @@
     "updateSuccess": "Textbook updated successfully.",
     "updateFailed": "Failed to update textbook.",
     "deleteSuccess": "Textbook deleted successfully.",
-    "deleteFailed": "Failed to delete textbook.",
+    "textbookDeleteFailed": "Failed to delete textbook.",
     "chapterCreateSuccess": "Chapter created successfully",
     "chapterCreateFailed": "Failed to create chapter",
     "chapterDeleteSuccess": "Chapter deleted successfully",
@@ -181,6 +196,57 @@
     "invalidContent": "Invalid chapter content data",
     "errorOccurred": "An error occurred",
     "deleteFailed": "Deletion failed",
-    "updateFailedGeneric": "Update failed"
+    "updateFailedGeneric": "Update failed",
+    "chapterNotBelong": "Chapter does not belong to this textbook",
+    "kpNotBelong": "Knowledge point does not belong to this textbook",
+    "chaptersReordered": "Chapters reordered successfully",
+    "ok": "OK",
+    "kpLoadFailed": "Failed to load knowledge points",
+    "graphLoadFailed": "Graph failed to load",
+    "invalidInput": "Invalid input",
+    "cyclicDependency": "Cannot add cyclic dependency",
+    "prerequisiteCreated": "Prerequisite added",
+    "prerequisiteCreateFailed": "Failed to add prerequisite",
+    "prerequisiteDeleted": "Prerequisite removed",
+    "prerequisiteDeleteFailed": "Failed to remove prerequisite"
+  },
+  "graph": {
+    "viewMode": {
+      "structure": "Structure",
+      "studentMastery": "My Mastery",
+      "classMastery": "Class Mastery"
+    },
+    "node": {
+      "questions": "Questions",
+      "mastery": "Mastery",
+      "prerequisite": "Prerequisite",
+      "successor": "Successor"
+    },
+    "detail": {
+      "title": "Knowledge Point Details",
+      "noDescription": "No description",
+      "viewAllQuestions": "View all questions",
+      "editPrerequisite": "Edit prerequisites",
+      "addPrerequisite": "Add prerequisite",
+      "removePrerequisite": "Remove",
+      "noPrerequisites": "No prerequisite knowledge points",
+      "noSuccessors": "No successor knowledge points",
+      "masteryNotAssessed": "Not assessed",
+      "correctRate": "Correct rate",
+      "totalQuestions": "Total questions"
+    },
+    "toolbar": {
+      "search": "Search knowledge points",
+      "filterByChapter": "Filter by chapter",
+      "resetView": "Reset view"
+    },
+    "empty": {
+      "noPrerequisites": "No prerequisite relationships",
+      "noData": "No graph data"
+    },
+    "error": {
+      "cyclicDependency": "Cannot add cyclic dependency",
+      "loadFailed": "Graph failed to load"
+    }
   }
 }