refactor: 优化全选逻辑和样式

app/src/main/kotlin/cn/super12138/todo/ui/pages/main/MainPage.kt

@@ -91,7 +91,7 @@ fun MainPage(
                 selectedTodoIds = selectedTodoIds,
                 selectedMode = !isSelectedIdsEmpty,
                 onCancelSelect = { viewModel.clearAllTodoSelection() },
-                onSelectAll = { viewModel.toggleAllSelected() },
+                onSelectAll = { viewModel.selectAllTodos() },
                 onDeleteSelectedTodo = { showDeleteConfirmDialog = true },
                 toSettingsPage = toSettingsPage
             )

app/src/main/kotlin/cn/super12138/todo/ui/pages/main/components/TodoCard.kt

@@ -120,7 +120,10 @@ fun TodoCard(
                             },
                             modifier = Modifier.padding(start = 5.dp)
                         ) {
-                            Text(priority.getDisplayName(context))
+                            Text(
+                                text = priority.getDisplayName(context),
+                                textDecoration = if (completed) TextDecoration.LineThrough else TextDecoration.None,
+                            )
                         }
                     }
                 ) {

app/src/main/kotlin/cn/super12138/todo/ui/viewmodels/MainViewModel.kt

@@ -116,19 +116,12 @@ class MainViewModel : ViewModel() {
     /**
      * 切换是否全选
      */
-    fun toggleAllSelected() {
+    fun selectAllTodos() {
         viewModelScope.launch {
             toDos.firstOrNull()?.let { todos ->
+                // 无论是否有选择都全选
                 val allIds = todos.map { it.id }
-                _selectedTodoIds.update { currentSelectedIds ->
-                    if (currentSelectedIds.containsAll(allIds)) {
-                        // 如果当前是全选状态，取消所有选择（切换为全不选）
-                        emptyList()
-                    } else {
-                        // 如果当前不是全选状态，选中所有项
-                        allIds
-                    }
-                }
+                _selectedTodoIds.value = allIds
             }
         }
     }