fix(ui): 认种页面省市选择器选择后禁用

- 首次选择省市后保存到本地存储
- 非首次进入时禁用省市选择器（不可重新选择）
- 添加"已锁定"标签和锁定图标显示禁用状态
- UI 显示灰色背景表示禁用

🤖 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

@@ -165,11 +165,19 @@ class _PlantingLocationPageState extends ConsumerState<PlantingLocationPage> {
 
   /// 显示省份选择器
   void _showProvinceSelector() {
+    // 如果已经保存过省市，则禁止重新选择
+    if (_hasSavedLocation) {
+      return;
+    }
     _showCityPicker();
   }
 
   /// 显示城市选择器
   void _showCitySelector() {
+    // 如果已经保存过省市，则禁止重新选择
+    if (_hasSavedLocation) {
+      return;
+    }
     _showCityPicker();
   }
 
@@ -387,32 +395,57 @@ class _PlantingLocationPageState extends ConsumerState<PlantingLocationPage> {
 
   /// 构建省份选择器
   Widget _buildProvinceSelector() {
+    final bool isDisabled = _hasSavedLocation;
+
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
         // 标签
-        const Text(
+        Row(
-          '省份（必选）',
+          children: [
-          style: TextStyle(
+            Text(
-            fontSize: 16,
+              '省份（必选）',
-            fontFamily: 'Inter',
+              style: TextStyle(
-            fontWeight: FontWeight.w500,
+                fontSize: 16,
-            height: 1.5,
+                fontFamily: 'Inter',
-            color: Color(0xFF5D4037),
+                fontWeight: FontWeight.w500,
-          ),
+                height: 1.5,
+                color: isDisabled ? const Color(0xFF5D4037).withValues(alpha: 0.6) : const Color(0xFF5D4037),
+              ),
+            ),
+            if (isDisabled) ...[
+              const SizedBox(width: 8),
+              Container(
+                padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
+                decoration: BoxDecoration(
+                  color: const Color(0xFFD4AF37).withValues(alpha: 0.2),
+                  borderRadius: BorderRadius.circular(4),
+                ),
+                child: const Text(
+                  '已锁定',
+                  style: TextStyle(
+                    fontSize: 10,
+                    fontFamily: 'Inter',
+                    fontWeight: FontWeight.w500,
+                    color: Color(0xFFD4AF37),
+                  ),
+                ),
+              ),
+            ],
+          ],
         ),
         const SizedBox(height: 7),
         // 选择框
         GestureDetector(
-          onTap: _showProvinceSelector,
+          onTap: isDisabled ? null : _showProvinceSelector,
           child: Container(
             width: double.infinity,
             padding: const EdgeInsets.symmetric(horizontal: 17, vertical: 13),
             decoration: BoxDecoration(
-              color: Colors.white,
+              color: isDisabled ? const Color(0xFFF5F5F5) : Colors.white,
               borderRadius: BorderRadius.circular(8),
               border: Border.all(
-                color: const Color(0x4D8B5A2B),
+                color: isDisabled ? const Color(0x338B5A2B) : const Color(0x4D8B5A2B),
                 width: 1,
               ),
             ),
@@ -426,13 +459,13 @@ class _PlantingLocationPageState extends ConsumerState<PlantingLocationPage> {
                     fontFamily: 'Inter',
                     height: 1.5,
                     color: _selectedProvinceName != null
-                        ? const Color(0xFF5D4037)
+                        ? (isDisabled ? const Color(0xFF5D4037).withValues(alpha: 0.6) : const Color(0xFF5D4037))
                         : const Color(0xFF5D4037).withValues(alpha: 0.5),
                   ),
                 ),
-                const Icon(
+                Icon(
-                  Icons.keyboard_arrow_down,
+                  isDisabled ? Icons.lock_outline : Icons.keyboard_arrow_down,
-                  color: Color(0xFF8B5A2B),
+                  color: isDisabled ? const Color(0xFF8B5A2B).withValues(alpha: 0.5) : const Color(0xFF8B5A2B),
                   size: 24,
                 ),
               ],
@@ -445,32 +478,57 @@ class _PlantingLocationPageState extends ConsumerState<PlantingLocationPage> {
 
   /// 构建城市选择器
   Widget _buildCitySelector() {
+    final bool isDisabled = _hasSavedLocation;
+
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
         // 标签
-        const Text(
+        Row(
-          '市级（必选）',
+          children: [
-          style: TextStyle(
+            Text(
-            fontSize: 16,
+              '市级（必选）',
-            fontFamily: 'Inter',
+              style: TextStyle(
-            fontWeight: FontWeight.w500,
+                fontSize: 16,
-            height: 1.5,
+                fontFamily: 'Inter',
-            color: Color(0xFF5D4037),
+                fontWeight: FontWeight.w500,
-          ),
+                height: 1.5,
+                color: isDisabled ? const Color(0xFF5D4037).withValues(alpha: 0.6) : const Color(0xFF5D4037),
+              ),
+            ),
+            if (isDisabled) ...[
+              const SizedBox(width: 8),
+              Container(
+                padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
+                decoration: BoxDecoration(
+                  color: const Color(0xFFD4AF37).withValues(alpha: 0.2),
+                  borderRadius: BorderRadius.circular(4),
+                ),
+                child: const Text(
+                  '已锁定',
+                  style: TextStyle(
+                    fontSize: 10,
+                    fontFamily: 'Inter',
+                    fontWeight: FontWeight.w500,
+                    color: Color(0xFFD4AF37),
+                  ),
+                ),
+              ),
+            ],
+          ],
         ),
         const SizedBox(height: 7),
         // 选择框
         GestureDetector(
-          onTap: _showCitySelector,
+          onTap: isDisabled ? null : _showCitySelector,
           child: Container(
             width: double.infinity,
             padding: const EdgeInsets.symmetric(horizontal: 17, vertical: 13),
             decoration: BoxDecoration(
-              color: Colors.white,
+              color: isDisabled ? const Color(0xFFF5F5F5) : Colors.white,
               borderRadius: BorderRadius.circular(8),
               border: Border.all(
-                color: const Color(0x4D8B5A2B),
+                color: isDisabled ? const Color(0x338B5A2B) : const Color(0x4D8B5A2B),
                 width: 1,
               ),
             ),
@@ -484,13 +542,13 @@ class _PlantingLocationPageState extends ConsumerState<PlantingLocationPage> {
                     fontFamily: 'Inter',
                     height: 1.5,
                     color: _selectedCityName != null
-                        ? const Color(0xFF5D4037)
+                        ? (isDisabled ? const Color(0xFF5D4037).withValues(alpha: 0.6) : const Color(0xFF5D4037))
                         : const Color(0xFF5D4037).withValues(alpha: 0.5),
                   ),
                 ),
-                const Icon(
+                Icon(
-                  Icons.keyboard_arrow_down,
+                  isDisabled ? Icons.lock_outline : Icons.keyboard_arrow_down,
-                  color: Color(0xFF8B5A2B),
+                  color: isDisabled ? const Color(0xFF8B5A2B).withValues(alpha: 0.5) : const Color(0xFF8B5A2B),
                   size: 24,
                 ),
               ],