feat: AI 对话附件上下文解析 + 历史会话归档 + 多页面 UI 重构

- 后端: 新增 AttachmentContextBuilder 解析图片/PDF 摘要并拼入 LLM 上下文; ai_chat_endpoints 扩展附件接口; 新增 ReportAnalysisService
- 前端: 新增历史会话页与 conversation_history_provider; chat 链路支持附件展示与回放
- UI: 重构 medication_checkin / notification_center / profile / health_drawer 等多页面
- 配置: api_client baseUrl 适配当前 WiFi IP

health_app/lib/pages/diet/diet_capture_page.dart

@@ -358,7 +358,7 @@ class _DietCapturePageState extends ConsumerState<DietCapturePage> {
 
   Widget _buildResultView(BuildContext context, WidgetRef ref) {
     final state = ref.watch(dietProvider);
-    final screenW = MediaQuery.of(context).size.width;
+    final screenW = MediaQuery.sizeOf(context).width;
 
     return SingleChildScrollView(
       padding: const EdgeInsets.fromLTRB(16, 12, 16, 24),
@@ -388,16 +388,15 @@ class _DietCapturePageState extends ConsumerState<DietCapturePage> {
             const SizedBox(height: 16),
             if (state.isAnalyzing)
               _buildAnalyzing(state)
+            else if (state.foods.isEmpty)
+              _buildNoFoodHint()
             else ...[
-              if (state.foods.isNotEmpty) ...[
-                _buildFoodList(ref),
+              _buildFoodList(ref),
+              const SizedBox(height: 16),
+              _buildNutritionCard(ref),
+              if (state.commentary != null && state.commentary!.isNotEmpty) ...[
                 const SizedBox(height: 16),
-                _buildNutritionCard(ref),
-                if (state.commentary != null &&
-                    state.commentary!.isNotEmpty) ...[
-                  const SizedBox(height: 16),
-                  _buildAiCommentary(state.commentary!),
-                ],
+                _buildAiCommentary(state.commentary!),
               ],
               const SizedBox(height: 20),
               _buildSaveButton(),
@@ -498,6 +497,43 @@ class _DietCapturePageState extends ConsumerState<DietCapturePage> {
     );
   }
 
+  Widget _buildNoFoodHint() {
+    return Container(
+      width: double.infinity,
+      padding: const EdgeInsets.symmetric(vertical: 36, horizontal: 18),
+      decoration: BoxDecoration(
+        color: Colors.white,
+        borderRadius: BorderRadius.circular(18),
+        border: Border.all(color: AppColors.borderLight),
+        boxShadow: AppColors.cardShadowLight,
+      ),
+      child: Column(
+        children: [
+          const Icon(
+            Icons.image_not_supported_outlined,
+            size: 44,
+            color: AppColors.textHint,
+          ),
+          const SizedBox(height: 14),
+          const Text(
+            '未识别到食物',
+            style: TextStyle(
+              fontSize: 16,
+              fontWeight: FontWeight.w700,
+              color: AppColors.textPrimary,
+            ),
+          ),
+          const SizedBox(height: 6),
+          const Text(
+            '请重新拍摄或选择含有食物的清晰照片',
+            textAlign: TextAlign.center,
+            style: TextStyle(fontSize: 13, color: AppColors.textSecondary),
+          ),
+        ],
+      ),
+    );
+  }
+
   // ─────────── 食物列表 ───────────
   Widget _buildFoodList(WidgetRef ref) {
     final state = ref.watch(dietProvider);