fix(mobile): auto-show confirm dialog when planting location is saved

When user has previously saved province/city selection:
- Automatically show confirm dialog on page load
- Skip the 5-second countdown timer
- Hide countdown text in dialog when skipCountdown is true
- User can directly confirm and proceed with planting

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/mobile-app/lib/features/planting/presentation/pages/planting_location_page.dart

@@ -65,7 +65,10 @@ class _PlantingLocationPageState extends ConsumerState<PlantingLocationPage> {
   @override
   void initState() {
     super.initState();
-    _loadSavedLocation();
+    // 使用 WidgetsBinding 确保在 build 完成后执行
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      _loadSavedLocation();
+    });
   }
 
   /// 从本地存储加载保存的省市
@@ -87,12 +90,28 @@ class _PlantingLocationPageState extends ConsumerState<PlantingLocationPage> {
           _hasSavedLocation = true;
         });
         debugPrint('[PlantingLocationPage] 已加载保存的省市: $provinceName · $cityName');
+
+        // 如果有保存的省市，直接弹出确认弹窗（跳过倒计时）
+        _showConfirmDialogDirectly();
       }
     } catch (e) {
       debugPrint('[PlantingLocationPage] 加载省市失败: $e');
     }
   }
 
+  /// 直接显示确认弹窗（用于已保存省市的情况）
+  Future<void> _showConfirmDialogDirectly() async {
+    if (!mounted) return;
+
+    await PlantingConfirmDialog.show(
+      context: context,
+      province: _selectedProvinceName!,
+      city: _selectedCityName!,
+      skipCountdown: true,  // 跳过倒计时
+      onConfirm: _submitPlanting,
+    );
+  }
+
   /// 保存省市到本地存储
   Future<void> _saveLocation() async {
     if (_selectedProvinceName == null || _selectedProvinceCode == null ||

frontend/mobile-app/lib/features/planting/presentation/widgets/planting_confirm_dialog.dart

@@ -264,6 +264,11 @@ class _PlantingConfirmDialogState extends State<PlantingConfirmDialog> {
 
   /// 构建倒计时文字
   Widget _buildCountdownText() {
+    // 如果跳过倒计时，不显示倒计时文字
+    if (widget.skipCountdown) {
+      return const SizedBox(height: 16);
+    }
+
     return Padding(
       padding: const EdgeInsets.symmetric(vertical: 16),
       child: Text(