fix: 食物识别编辑框删除bug + VLM相关代码回滚

- 修复饮食识别结果编辑框一次只能删一个字的bug(控制器缓存)
- 回滚VLM图片压缩代码到原始状态
- 保持原有显示逻辑不变

health_app/lib/pages/diet/diet_capture_page.dart

@@ -593,6 +593,7 @@ class _DietCapturePageState extends ConsumerState<DietCapturePage> {
                   (v) => ref
                       .read(dietProvider.notifier)
                       .updateFoodName(food.id, v),
+                  fieldKey: '${food.id}_name',
                   style: const TextStyle(
                     fontSize: 17,
                     fontWeight: FontWeight.w600,
@@ -608,6 +609,7 @@ class _DietCapturePageState extends ConsumerState<DietCapturePage> {
                         (v) => ref
                             .read(dietProvider.notifier)
                             .updateFoodPortion(food.id, v),
+                        fieldKey: '${food.id}_portion',
                         hint: '份量',
                         style: const TextStyle(
                           fontSize: 14,
@@ -629,6 +631,7 @@ class _DietCapturePageState extends ConsumerState<DietCapturePage> {
                                     food.id,
                                     int.tryParse(v) ?? 0,
                                   ),
+                              fieldKey: '${food.id}_cal',
                               hint: '0',
                               style: const TextStyle(
                                 fontSize: 14,
@@ -664,16 +667,26 @@ class _DietCapturePageState extends ConsumerState<DietCapturePage> {
     );
   }
 
+  final Map<String, TextEditingController> _fieldCtrls = {};
+
+  TextEditingController _ctrlFor(String key, String value) {
+    if (_fieldCtrls.containsKey(key)) return _fieldCtrls[key]!;
+    final c = TextEditingController(text: value);
+    _fieldCtrls[key] = c;
+    return c;
+  }
+
   Widget _compactField(
     String value,
     ValueChanged<String> cb, {
+    required String fieldKey,
     String? hint,
     TextStyle? style,
     TextAlign align = TextAlign.start,
     TextInputType? keyboardType,
   }) {
     return TextField(
-      controller: TextEditingController(text: value),
+      controller: _ctrlFor(fieldKey, value),
       onChanged: cb,
       keyboardType: keyboardType,
       textAlign: align,