feat(lesson-preparation): major update with AI features, schedules, and new components

- Add actions-schedules.ts and data-access-schedules.ts for schedule management

- Add AI differentiation, AI feedback, consistency check dialogs

- Add attachment-picker, curriculum-heatmap, print-view, version-diff-view

- Add lesson-plan-mobile-view and schedule-dialog components

- Add lib: ai-differentiation, ai-feedback, auto-layout, consistency-check,

  curriculum-coverage, export, version-diff

- Add history-slice hook for version history

- Update existing components, hooks, providers, services, types

- Add teacher lesson-plans heatmap and library pages

src/modules/lesson-preparation/lib/auto-layout.ts

@@ -0,0 +1,82 @@
+/**
+ * V5-8：画布自动布局
+ *
+ * 使用 dagre 计算 DAG 布局，将教学节点按流程关系自动排列。
+ * 仅对可拖动的教学节点（非正文节点）布局，正文节点位置保持不变。
+ */
+import dagre from "@dagrejs/dagre";
+import type {
+  AnyLessonPlanNode,
+  AnyLessonPlanEdge,
+} from "../types";
+
+export interface AutoLayoutOptions {
+  /** 布局方向：TB（上→下）/ LR（左→右），默认 TB */
+  direction?: "TB" | "LR";
+  /** 节点宽度，默认 240 */
+  nodeWidth?: number;
+  /** 节点高度，默认 120 */
+  nodeHeight?: number;
+  /** 节点水平间距，默认 40 */
+  rankSep?: number;
+  /** 节点垂直间距，默认 60 */
+  nodeSep?: number;
+}
+
+/**
+ * 计算自动布局，返回每个节点的新位置（含原始位置作为兜底）
+ */
+export function computeAutoLayout(
+  nodes: AnyLessonPlanNode[],
+  edges: AnyLessonPlanEdge[],
+  options: AutoLayoutOptions = {},
+): Map<string, { x: number; y: number }> {
+  const {
+    direction = "TB",
+    nodeWidth = 240,
+    nodeHeight = 120,
+    rankSep = 60,
+    nodeSep = 40,
+  } = options;
+
+  const result = new Map<string, { x: number; y: number }>();
+
+  if (nodes.length === 0) return result;
+
+  const g = new dagre.graphlib.Graph();
+  g.setGraph({ rankdir: direction, ranksep: rankSep, nodesep: nodeSep });
+  g.setDefaultEdgeLabel(() => ({}));
+
+  // 仅对教学节点布局（正文节点固定位置）
+  const layoutableNodes = nodes.filter((n) => n.type !== "textbook_content");
+  const layoutableIds = new Set(layoutableNodes.map((n) => n.id));
+
+  for (const node of layoutableNodes) {
+    g.setNode(node.id, { width: nodeWidth, height: nodeHeight });
+  }
+
+  // 仅添加两端都可布局的 flow 边
+  for (const edge of edges) {
+    if (edge.type !== "flow") continue;
+    if (!layoutableIds.has(edge.source) || !layoutableIds.has(edge.target)) continue;
+    g.setEdge(edge.source, edge.target);
+  }
+
+  // 孤立节点（无边）也要 setNode，dagre 会自动排列
+  dagre.layout(g);
+
+  for (const node of layoutableNodes) {
+    const laid = g.node(node.id);
+    if (laid) {
+      // dagre 返回中心点，React Flow 使用左上角，需减去半宽/半高
+      result.set(node.id, {
+        x: laid.x - nodeWidth / 2,
+        y: laid.y - nodeHeight / 2,
+      });
+    } else {
+      result.set(node.id, node.position);
+    }
+  }
+
+  return result;
+}