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/modules/textbooks/components/graph-node-detail-panel.tsx

@@ -0,0 +1,182 @@
+"use client"
+
+import { useTranslations } from "next-intl"
+import Link from "next/link"
+import { X, ExternalLink, Plus, Trash2 } from "lucide-react"
+import { Button } from "@/shared/components/ui/button"
+import { Badge } from "@/shared/components/ui/badge"
+import { ScrollArea } from "@/shared/components/ui/scroll-area"
+import { Separator } from "@/shared/components/ui/separator"
+import type { KpWithRelations, MasteryInfo } from "../types"
+
+interface GraphNodeDetailPanelProps {
+  kp: KpWithRelations
+  mastery: MasteryInfo | null
+  prerequisites: { id: string; name: string; description: string | null }[]
+  successors: { id: string; name: string; description: string | null }[]
+  canEdit: boolean
+  textbookId: string
+  onClose: () => void
+  onJumpToKp: (kpId: string) => void
+  onAddPrerequisite: () => void
+  onRemovePrerequisite: (prereqId: string) => void
+}
+
+export function GraphNodeDetailPanel({
+  kp,
+  mastery,
+  prerequisites,
+  successors,
+  canEdit,
+  onClose,
+  onJumpToKp,
+  onAddPrerequisite,
+  onRemovePrerequisite,
+}: GraphNodeDetailPanelProps) {
+  const t = useTranslations("textbooks")
+
+  const correctRate = mastery && mastery.totalQuestions > 0
+    ? Math.round((mastery.correctQuestions / mastery.totalQuestions) * 100)
+    : null
+
+  return (
+    <div className="flex flex-col h-full border-l bg-background">
+      <div className="flex items-center justify-between p-3 border-b shrink-0">
+        <h3 className="text-sm font-semibold truncate">{t("graph.detail.title")}</h3>
+        <Button variant="ghost" size="sm" className="h-7 w-7 p-0" onClick={onClose}>
+          <X className="h-4 w-4" />
+        </Button>
+      </div>
+
+      <ScrollArea className="flex-1 min-h-0">
+        <div className="p-3 space-y-4">
+          {/* 知识点名称 */}
+          <div>
+            <h4 className="text-base font-medium">{kp.name}</h4>
+            {kp.chapterTitle && (
+              <p className="text-xs text-muted-foreground mt-1">{kp.chapterTitle}</p>
+            )}
+          </div>
+
+          {/* 描述 */}
+          <div>
+            <h5 className="text-xs font-medium text-muted-foreground mb-1">
+              {t("graph.detail.title")}
+            </h5>
+            <p className="text-sm">
+              {kp.description || t("graph.detail.noDescription")}
+            </p>
+          </div>
+
+          {/* 掌握度 */}
+          {mastery && (
+            <>
+              <Separator />
+              <div>
+                <h5 className="text-xs font-medium text-muted-foreground mb-2">
+                  {t("graph.node.mastery")}
+                </h5>
+                <div className="space-y-1 text-sm">
+                  <div className="flex justify-between">
+                    <span>{t("graph.detail.correctRate")}</span>
+                    <span>{correctRate !== null ? `${correctRate}%` : t("graph.detail.masteryNotAssessed")}</span>
+                  </div>
+                  <div className="flex justify-between">
+                    <span>{t("graph.detail.totalQuestions")}</span>
+                    <span>{mastery.totalQuestions}</span>
+                  </div>
+                </div>
+              </div>
+            </>
+          )}
+
+          {/* 关联题目 */}
+          <Separator />
+          <div>
+            <div className="flex items-center justify-between mb-2">
+              <h5 className="text-xs font-medium text-muted-foreground">
+                {t("graph.node.questions")} ({kp.questionCount})
+              </h5>
+              {kp.questionCount > 0 && (
+                <Button asChild variant="ghost" size="sm" className="h-7 text-xs">
+                  <Link href={`/teacher/questions?kp=${kp.id}`}>
+                    <ExternalLink className="h-3 w-3 mr-1" />
+                    {t("graph.detail.viewAllQuestions")}
+                  </Link>
+                </Button>
+              )}
+            </div>
+          </div>
+
+          {/* 前置知识点 */}
+          <Separator />
+          <div>
+            <div className="flex items-center justify-between mb-2">
+              <h5 className="text-xs font-medium text-muted-foreground">
+                {t("graph.node.prerequisite")} ({prerequisites.length})
+              </h5>
+              {canEdit && (
+                <Button variant="ghost" size="sm" className="h-7 text-xs" onClick={onAddPrerequisite}>
+                  <Plus className="h-3 w-3 mr-1" />
+                  {t("graph.detail.addPrerequisite")}
+                </Button>
+              )}
+            </div>
+            {prerequisites.length === 0 ? (
+              <p className="text-xs text-muted-foreground">{t("graph.detail.noPrerequisites")}</p>
+            ) : (
+              <div className="space-y-1">
+                {prerequisites.map((p) => (
+                  <div key={p.id} className="flex items-center justify-between gap-2">
+                    <Button
+                      variant="ghost"
+                      size="sm"
+                      className="h-7 text-xs justify-start flex-1"
+                      onClick={() => onJumpToKp(p.id)}
+                    >
+                      {p.name}
+                    </Button>
+                    {canEdit && (
+                      <Button
+                        variant="ghost"
+                        size="sm"
+                        className="h-7 w-7 p-0 text-muted-foreground hover:text-destructive"
+                        onClick={() => onRemovePrerequisite(p.id)}
+                      >
+                        <Trash2 className="h-3 w-3" />
+                      </Button>
+                    )}
+                  </div>
+                ))}
+              </div>
+            )}
+          </div>
+
+          {/* 后置知识点 */}
+          <Separator />
+          <div>
+            <h5 className="text-xs font-medium text-muted-foreground mb-2">
+              {t("graph.node.successor")} ({successors.length})
+            </h5>
+            {successors.length === 0 ? (
+              <p className="text-xs text-muted-foreground">{t("graph.detail.noSuccessors")}</p>
+            ) : (
+              <div className="flex flex-wrap gap-1">
+                {successors.map((s) => (
+                  <Badge
+                    key={s.id}
+                    variant="outline"
+                    className="cursor-pointer hover:bg-accent text-xs"
+                    onClick={() => onJumpToKp(s.id)}
+                  >
+                    {s.name}
+                  </Badge>
+                ))}
+              </div>
+            )}
+          </div>
+        </div>
+      </ScrollArea>
+    </div>
+  )
+}