refactor: 4层架构重构 + 饮食VLM接入 + 多项修复

- 后端: remaining_endpoints拆分为6个独立文件
- 后端: AI Agent Handler从ai_chat_endpoints抽取为7个独立处理器
- 后端: 食物识别prompt改为输出结构化JSON
- 前端: 饮食识别从Mock替换为真实VLM API调用
- 前端: 首页图片上传URL修复(/api/upload→/api/files/upload)
- 前端: 拍饮食按钮导航到独立DietCapturePage
- 前端: 删除无用agent_bar.dart
- 前端: 修复widget_test.dart过期属性名
- 前端: 恢复ServicePackageCard和详情页
- 新增6份实施文档(情况/问诊/报告/建档/日历/视觉统一)

health_app/lib/widgets/agent_bar.dart

@@ -1,61 +0,0 @@
-import 'package:flutter/material.dart';
-import 'package:flutter_riverpod/flutter_riverpod.dart';
-import '../providers/chat_provider.dart';
-
-/// 智能体胶囊栏——横向滑动
-class AgentBar extends ConsumerWidget {
-  const AgentBar({super.key});
-
-  @override
-  Widget build(BuildContext context, WidgetRef ref) {
-    final selected = ref.watch(selectedAgentProvider);
-    final chatNotifier = ref.read(chatProvider.notifier);
-
-    void onTap(ActiveAgent agent) {
-      final notifier = ref.read(selectedAgentProvider.notifier);
-      notifier.select(agent == selected ? null : agent);
-      chatNotifier.setAgent(agent);
-    }
-
-    return Container(
-      height: 48,
-      color: Colors.white,
-      child: ListView(
-        scrollDirection: Axis.horizontal,
-        padding: const EdgeInsets.symmetric(horizontal: 12),
-        children: [
-          _buildCapsule('AI问诊', Icons.medical_services, ActiveAgent.consultation, selected, onTap),
-          _buildCapsule('记数据', Icons.edit_note, ActiveAgent.health, selected, onTap),
-          _buildCapsule('拍饮食', Icons.restaurant, ActiveAgent.diet, selected, onTap),
-          _buildCapsule('药管家', Icons.medication, ActiveAgent.medication, selected, onTap),
-          _buildCapsule('看报告', Icons.description, ActiveAgent.report, selected, onTap),
-          _buildCapsule('运动计划', Icons.fitness_center, ActiveAgent.exercise, selected, onTap),
-        ],
-      ),
-    );
-  }
-
-  Widget _buildCapsule(String label, IconData icon, ActiveAgent agent, ActiveAgent? selected, void Function(ActiveAgent) onTap) {
-    final isSelected = selected == agent;
-    return GestureDetector(
-      onTap: () => onTap(agent),
-      child: Container(
-        margin: const EdgeInsets.symmetric(horizontal: 4, vertical: 6),
-        padding: const EdgeInsets.symmetric(horizontal: 14),
-        decoration: BoxDecoration(
-          color: isSelected ? const Color(0xFF8B9CF7) : Colors.white,
-          border: Border.all(color: const Color(0xFF8B9CF7)),
-          borderRadius: BorderRadius.circular(24),
-        ),
-        child: Row(
-          mainAxisSize: MainAxisSize.min,
-          children: [
-            Icon(icon, size: 16, color: isSelected ? Colors.white : const Color(0xFF8B9CF7)),
-            const SizedBox(width: 6),
-            Text(label, style: TextStyle(fontSize: 13, color: isSelected ? Colors.white : const Color(0xFF8B9CF7))),
-          ],
-        ),
-      ),
-    );
-  }
-}