feat(app): 编辑器增强 — 查看模式 + 图层排序 + 标签/贴纸动态化

- EditorPage 新增查看模式: 打开已保存日记默认只读，编辑按钮切换
- EditorBloc 新增 ElementLayerChanged 事件，支持置顶/置底图层排序
- DraggableElement 添加图层控制按钮 (置顶/置底/删除)
- TagPanel 标签建议改为从日记历史动态生成 (Top 10 频率)
- StickerPickerSheet 重构，预留 API 扩展点

app/lib/features/editor/views/editor_page.dart

@@ -334,15 +334,26 @@ class _EditorView extends StatefulWidget {
 }
 
 class _EditorViewState extends State<_EditorView> {
+  /// 查看模式：打开已有日记时默认只读，点击"编辑"后进入编辑模式
+  bool _isViewMode = false;
+
   @override
   void initState() {
     super.initState();
-    // 当 journalId 非空时，从 Isar 加载已有日记数据
+    // 当 journalId 非空时，进入查看模式
+    _isViewMode = widget.journalId != null;
     if (widget.journalId != null) {
       _loadExistingJournal(widget.journalId!);
     }
   }
 
+  /// 从查看模式切换到编辑模式
+  void _enterEditMode() {
+    setState(() => _isViewMode = false);
+    // 切换到画笔工具，进入编辑状态
+    context.read<EditorBloc>().add(ToolChanged(EditorTool.brush));
+  }
+
   /// 从 Isar 加载已有日记 — 使用 LoadJournal 原子事件一次性还原
   Future<void> _loadExistingJournal(String id) async {
     try {
@@ -381,6 +392,11 @@ class _EditorViewState extends State<_EditorView> {
         elements: otherElements,
         lastSavedAt: entry.updatedAt,
       ));
+
+      // 查看模式下使用 select 工具，避免自动弹出画笔面板
+      if (_isViewMode) {
+        context.read<EditorBloc>().add(ToolChanged(EditorTool.select));
+      }
     } catch (e) {
       debugPrint('加载日记数据失败: $e');
     }
@@ -405,26 +421,31 @@ class _EditorViewState extends State<_EditorView> {
           Expanded(
             child: BlocBuilder<EditorBloc, EditorState>(
               builder: (context, state) {
-                return _EditorStack(state: state, journalId: widget.journalId);
+                return _EditorStack(
+                  state: state,
+                  journalId: widget.journalId,
+                  isViewMode: _isViewMode,
+                );
               },
             ),
           ),
 
-          // 底部工具栏（自带底部安全区）
-          BlocBuilder<EditorBloc, EditorState>(
-            builder: (context, state) {
-              return EditorToolbar(
-                state: state,
-                onEvent: (event) => context.read<EditorBloc>().add(event),
-              );
-            },
-          ),
+          // 底部工具栏 — 仅编辑模式显示
+          if (!_isViewMode)
+            BlocBuilder<EditorBloc, EditorState>(
+              builder: (context, state) {
+                return EditorToolbar(
+                  state: state,
+                  onEvent: (event) => context.read<EditorBloc>().add(event),
+                );
+              },
+            ),
         ],
       ),
     );
   }
 
-  /// 顶部操作栏 — 日期/撤销重做/标签/心情/完成
+  /// 顶部操作栏 — 查看模式: 返回/日期/评语/编辑按钮；编辑模式: 返回/日期/撤销重做/标签/完成
   Widget _buildTopBar(BuildContext context, EditorState state) {
     final colorScheme = Theme.of(context).colorScheme;
     return Container(
@@ -467,51 +488,67 @@ class _EditorViewState extends State<_EditorView> {
                       ),
                     ),
                   ),
-                  // 撤销
-                  IconButton(
-                    icon: const Icon(Icons.undo_rounded, size: 18),
-                    onPressed: () => context.read<EditorBloc>().add(Undo()),
-                    constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
-                  ),
-                  // 重做
-                  IconButton(
-                    icon: const Icon(Icons.redo_rounded, size: 18),
-                    onPressed: () => context.read<EditorBloc>().add(Redo()),
-                    constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
-                  ),
-                  // 自动保存状态
-                  _buildAutosaveIndicator(state),
-                  // 标签按钮
-                  IconButton(
-                    icon: const Icon(Icons.sell_rounded, size: 18),
-                    onPressed: () => _showTagPanel(context, state),
-                    constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
-                  ),
-                  // 评语按钮（仅已有日记显示）
-                  if (widget.journalId != null)
+                  if (_isViewMode) ...[
+                    // 查看模式：评语按钮 + 编辑按钮
+                    if (widget.journalId != null)
+                      IconButton(
+                        icon: const Icon(Icons.chat_bubble_outline_rounded, size: 18),
+                        onPressed: () => _showComments(context),
+                        constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
+                      ),
+                    Padding(
+                      padding: const EdgeInsets.only(left: 4),
+                      child: FilledButton.tonal(
+                        onPressed: _enterEditMode,
+                        style: FilledButton.styleFrom(
+                          padding: const EdgeInsets.symmetric(horizontal: 16),
+                          minimumSize: const Size(0, 32),
+                        ),
+                        child: const Text('编辑', style: TextStyle(fontSize: 14)),
+                      ),
+                    ),
+                  ] else ...[
+                    // 编辑模式：撤销/重做/标签/评语/完成
                     IconButton(
-                      icon: const Icon(Icons.chat_bubble_outline_rounded, size: 18),
-                      onPressed: () => _showComments(context),
+                      icon: const Icon(Icons.undo_rounded, size: 18),
+                      onPressed: () => context.read<EditorBloc>().add(Undo()),
                       constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
                     ),
-                  // 完成/保存按钮
-                  Padding(
-                    padding: const EdgeInsets.only(left: 4),
-                    child: FilledButton.tonal(
-                      onPressed: () => _handleSave(context, state),
-                      style: FilledButton.styleFrom(
-                        padding: const EdgeInsets.symmetric(horizontal: 16),
-                        minimumSize: const Size(0, 32),
-                      ),
-                      child: const Text('完成', style: TextStyle(fontSize: 14)),
+                    IconButton(
+                      icon: const Icon(Icons.redo_rounded, size: 18),
+                      onPressed: () => context.read<EditorBloc>().add(Redo()),
+                      constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
                     ),
-                  ),
+                    _buildAutosaveIndicator(state),
+                    IconButton(
+                      icon: const Icon(Icons.sell_rounded, size: 18),
+                      onPressed: () => _showTagPanel(context, state),
+                      constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
+                    ),
+                    if (widget.journalId != null)
+                      IconButton(
+                        icon: const Icon(Icons.chat_bubble_outline_rounded, size: 18),
+                        onPressed: () => _showComments(context),
+                        constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
+                      ),
+                    Padding(
+                      padding: const EdgeInsets.only(left: 4),
+                      child: FilledButton.tonal(
+                        onPressed: () => _handleSave(context, state),
+                        style: FilledButton.styleFrom(
+                          padding: const EdgeInsets.symmetric(horizontal: 16),
+                          minimumSize: const Size(0, 32),
+                        ),
+                        child: const Text('完成', style: TextStyle(fontSize: 14)),
+                      ),
+                    ),
+                  ],
                 ],
               ),
             ),
           ),
-          // 日期 + 心情条 (40px)
-          _buildDateMoodStrip(context, state),
+          // 日期 + 心情条 (40px) — 仅编辑模式显示
+          if (!_isViewMode) _buildDateMoodStrip(context, state),
         ],
       ),
     );
@@ -674,8 +711,13 @@ class _EditorViewState extends State<_EditorView> {
 class _EditorStack extends StatefulWidget {
   final EditorState state;
   final String? journalId;
+  final bool isViewMode;
 
-  const _EditorStack({required this.state, this.journalId});
+  const _EditorStack({
+    required this.state,
+    this.journalId,
+    this.isViewMode = false,
+  });
 
   @override
   State<_EditorStack> createState() => _EditorStackState();
@@ -900,6 +942,7 @@ class _EditorStackState extends State<_EditorStack> {
                 padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 8),
                 child: TextField(
                   controller: _titleController,
+                  enabled: !widget.isViewMode,
                   style: TextStyle(
                     fontFamily: 'Quicksand',
                     fontSize: 18,
@@ -943,8 +986,8 @@ class _EditorStackState extends State<_EditorStack> {
         if (state.elements.isNotEmpty)
           _buildElementLayer(context, state),
 
-        // 文字输入覆盖层（文字工具激活时显示）
-        if (state.activeTool == EditorTool.text)
+        // 文字输入覆盖层（文字工具激活时显示）— 仅编辑模式
+        if (!widget.isViewMode && state.activeTool == EditorTool.text)
           TextInputOverlay(
             onConfirmed: (text, fontSize, fontColor) {
               final center = Offset(
@@ -967,8 +1010,8 @@ class _EditorStackState extends State<_EditorStack> {
             },
           ),
 
-        // 图片选择覆盖层（图片工具激活时显示）
-        if (state.activeTool == EditorTool.photo)
+        // 图片选择覆盖层（图片工具激活时显示）— 仅编辑模式
+        if (!widget.isViewMode && state.activeTool == EditorTool.photo)
           Center(
             child: Row(
               mainAxisAlignment: MainAxisAlignment.center,
@@ -988,8 +1031,11 @@ class _EditorStackState extends State<_EditorStack> {
             ),
           ),
 
-        // 空状态提示
-        if (state.strokes.isEmpty && state.elements.isEmpty && state.activeTool == EditorTool.select)
+        // 空状态提示 — 仅编辑模式显示
+        if (!widget.isViewMode &&
+            state.strokes.isEmpty &&
+            state.elements.isEmpty &&
+            state.activeTool == EditorTool.select)
           _buildEmptyHint(context),
       ],
     );
@@ -1057,6 +1103,11 @@ class _EditorStackState extends State<_EditorStack> {
           onDeleted: (id) {
             context.read<EditorBloc>().add(ElementRemoved(id));
           },
+          onLayerChanged: (id, change) {
+            context.read<EditorBloc>().add(
+              ElementLayerChanged(elementId: id, change: change),
+            );
+          },
         );
       }).toList(),
     );