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/providers/conversation_history_provider.dart

@@ -0,0 +1,85 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../providers/auth_provider.dart';
+import '../providers/chat_provider.dart';
+
+/// 对话历史列表项
+class ConversationListItem {
+  final String id;
+  final String? title;
+  final String? summary;
+  final int messageCount;
+  final DateTime updatedAt;
+
+  const ConversationListItem({
+    required this.id,
+    this.title,
+    this.summary,
+    required this.messageCount,
+    required this.updatedAt,
+  });
+
+  factory ConversationListItem.fromJson(Map<String, dynamic> json) =>
+      ConversationListItem(
+        id: json['id']?.toString() ?? '',
+        title: json['title']?.toString(),
+        summary: json['summary']?.toString(),
+        messageCount: (json['messageCount'] as num?)?.toInt() ?? 0,
+        updatedAt: DateTime.tryParse(json['updatedAt']?.toString() ?? '') ??
+            DateTime.now(),
+      );
+}
+
+/// 对话历史 Notifier：缓存列表，提供刷新/删除/清空。
+class ConversationHistoryNotifier
+    extends AsyncNotifier<List<ConversationListItem>> {
+  @override
+  Future<List<ConversationListItem>> build() => _fetch();
+
+  Future<List<ConversationListItem>> _fetch() async {
+    final api = ref.read(apiClientProvider);
+    final res = await api.get('/api/ai/conversations');
+    final raw = (res.data['data'] as List?) ?? const [];
+    return raw
+        .whereType<Map>()
+        .map((m) => ConversationListItem.fromJson(Map<String, dynamic>.from(m)))
+        .toList();
+  }
+
+  Future<void> refresh() async {
+    state = const AsyncValue.loading();
+    state = await AsyncValue.guard(_fetch);
+  }
+
+  /// 删除单条；先乐观更新 UI，失败回滚。
+  Future<void> deleteOne(String id) async {
+    final previous = state.asData?.value ?? const <ConversationListItem>[];
+    state = AsyncValue.data(previous.where((e) => e.id != id).toList());
+    try {
+      final api = ref.read(apiClientProvider);
+      await api.delete('/api/ai/conversations/$id');
+    } catch (_) {
+      state = AsyncValue.data(previous);
+      rethrow;
+    }
+    // 同步清掉当前 chat state（如果删的就是当前会话）
+    final chat = ref.read(chatProvider);
+    if (chat.conversationId == id) {
+      ref.read(chatProvider.notifier).resetSession();
+    }
+  }
+
+  /// 一键清空当前用户的全部对话。
+  Future<int> clearAll() async {
+    final api = ref.read(apiClientProvider);
+    final res = await api.delete('/api/ai/conversations');
+    state = const AsyncValue.data([]);
+    ref.read(chatProvider.notifier).resetSession();
+    final deleted = res.data['data']?['deleted'];
+    return deleted is num ? deleted.toInt() : 0;
+  }
+}
+
+final conversationHistoryProvider = AsyncNotifierProvider<
+    ConversationHistoryNotifier, List<ConversationListItem>>(
+  ConversationHistoryNotifier.new,
+);