feat(app): add error/loading boundaries and update dashboard routes

- Add error.tsx and loading.tsx boundaries for admin, parent, student, teacher routes

- Add dashboard-error-fallback and dashboard-loading-skeleton components

- Add student/learning page, parent/leave routes, teacher textbook components

- Update existing app routes across auth, dashboard, and API endpoints

- Update proxy middleware and next-auth type declarations

src/app/globals.css

@@ -190,3 +190,54 @@
     font-feature-settings: "rlig" 1, "calt" 1;
   }
 }
+
+/* ---- 备课画布：锚点与连线透明度规则 ---- */
+/* 范围锚定文本背景：默认透明（opacity 0），选中关联节点时显示（opacity 0.3） */
+.range-anchor {
+  background-color: var(--node-color, #1976d2);
+  opacity: 0;
+  transition: opacity 0.2s ease;
+  border-radius: 2px;
+  cursor: pointer;
+  padding: 0 1px;
+}
+.range-anchor.active {
+  opacity: 0.3;
+}
+.range-anchor:hover {
+  opacity: 0.5;
+}
+
+/* 点锚定占位符：默认半透明（opacity 0.3），选中关联节点时不透明（opacity 1） */
+.point-anchor {
+  background-color: var(--node-color, #1976d2);
+  color: #fff;
+  opacity: 0.3;
+  transition: opacity 0.2s ease;
+  border-radius: 50%;
+  cursor: pointer;
+  padding: 0 4px;
+  margin: 0 1px;
+  font-size: 0.85em;
+  font-weight: 600;
+  display: inline-block;
+  min-width: 1.2em;
+  text-align: center;
+  line-height: 1.2;
+  user-select: none;
+}
+.point-anchor.active {
+  opacity: 1;
+}
+.point-anchor:hover {
+  opacity: 0.8;
+}
+
+/* 锚点连线：默认 10% 透明度，选中关联节点时完整显示 */
+.anchor-edge {
+  opacity: 0.1;
+  transition: opacity 0.2s ease;
+}
+.anchor-edge.active {
+  opacity: 1;
+}