refactor(lesson-preparation): 配色统一到中性令牌（移除 Material 鲜艳色）

src/app/globals.css

@@ -48,23 +48,38 @@
   --chart-5: 27 87% 67%;
 
   /* Lesson Plan Node Colors (V4 P1-4 修复：从硬编码提取到设计令牌) */
-  --lesson-node-objective: #4caf50;
-  --lesson-node-key-point: #f44336;
-  --lesson-node-import: #2196f3;
-  --lesson-node-new-teaching: #9c27b0;
-  --lesson-node-consolidation: #ff9800;
-  --lesson-node-summary: #607d8b;
-  --lesson-node-homework: #795548;
-  --lesson-node-blackboard: #009688;
-  --lesson-node-text-study: #3f51b5;
-  --lesson-node-exercise: #e91e63;
-  --lesson-node-rich-text: #9e9e9e;
-  --lesson-node-reflection: #cddc39;
-  --lesson-node-textbook-content: #455a64;
-  --lesson-node-selected: #1976d2;
-  --lesson-node-default: #9e9e9e;
-  --lesson-canvas-bg: #ccc;
-  
+  /* V4 纸感重构：原 --lesson-node-* 已删除，改为 --lp-dot-* 中性色点令牌 */
+
+  /* V4 备课编辑器：纸感令牌（替代 --lesson-node-*） */
+  --lp-paper: #fefefe;
+  --lp-paper-edge: #f8f8f7;
+  --lp-paper-shadow: 0 1px 2px rgba(15,15,15,0.04), 0 8px 24px rgba(15,15,15,0.04);
+  --lp-paper-shadow-active: 0 1px 2px rgba(15,15,15,0.06), 0 12px 36px rgba(15,15,15,0.08);
+  --lp-anchor-range: rgba(28, 25, 23, 0.08);
+  --lp-anchor-range-active: rgba(28, 25, 23, 0.16);
+  --lp-anchor-point: #1c1917;
+  --lp-inline-node-border: #d6d3d1;
+  --lp-inline-node-text: #44403c;
+  --lp-inline-node-meta: #a8a29e;
+  --lp-interaction: #6366f1;
+
+  /* V4 节点类型色点（极克制） */
+  --lp-dot-objective: #4b5563;
+  --lp-dot-key-point: #525252;
+  --lp-dot-import: #6b7280;
+  --lp-dot-new-teaching: #1c1917;
+  --lp-dot-consolidation: #6b7280;
+  --lp-dot-summary: #525252;
+  --lp-dot-homework: #525252;
+  --lp-dot-blackboard: #44403c;
+  --lp-dot-text-study: #4b5563;
+  --lp-dot-exercise: #6b7280;
+  --lp-dot-rich-text: #a8a29e;
+  --lp-dot-reflection: #6b7280;
+  --lp-dot-interaction: #6366f1;
+  --lp-dot-textbook: #44403c;
+  --lp-dot-default: #a8a29e;
+
   /* Sidebar Specific */
   --sidebar-background: 0 0% 98%;
   --sidebar-foreground: 240 5.3% 26.1%;