fix(app): Phase 1.1 紧急修复 — SyncEngine 接入 + authorId + catch 异常处理

- feat(sync): SyncEngine 接入 EditorPage, 保存时 enqueue + 网络恢复自动 trySync
- fix(editor): authorId 从 AuthBloc 获取, 替代硬编码 'local'
- fix(bloc): class_bloc/calendar/profile/parent catch(_).全部改为 debugPrint
- feat(editor): 编辑器工具栏拆分 (brush_panel/tag_panel/text_format_bar/dot_grid_painter)
- feat(editor): EditorBloc 扩展 + EditorPage 增强
- feat(search): SearchBloc 扩展搜索功能
- feat(home): HomeBloc/HomePage 增强
- feat(auth): LoginPage 增强
- feat(templates): TemplateGalleryPage 重构
- fix(web): 管理端班级/日记页面修复
- fix(server): comment_service + theme_handler 修复
- docs: 添加全链路审计报告和验证截图

app/lib/features/editor/widgets/dot_grid_painter.dart

@@ -0,0 +1,28 @@
+// 点阵背景画笔 — 24x24px 间距，1px 圆点
+// 用于日记编辑区域提供纸质感背景
+
+import 'package:flutter/material.dart';
+
+/// 点阵背景画笔 -- 24x24px 间距，1px 圆点
+class DotGridPainter extends CustomPainter {
+  const DotGridPainter();
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    final paint = Paint()
+      ..color = const Color(0xFF2D2420).withOpacity(0.15)
+      ..style = PaintingStyle.fill;
+
+    const spacing = 24.0;
+    const dotRadius = 1.0;
+
+    for (double x = spacing; x < size.width; x += spacing) {
+      for (double y = spacing; y < size.height; y += spacing) {
+        canvas.drawCircle(Offset(x, y), dotRadius, paint);
+      }
+    }
+  }
+
+  @override
+  bool shouldRepaint(covariant DotGridPainter oldDelegate) => false;
+}