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/utils/sse_handler.dart

@@ -10,6 +10,8 @@ class SseHandler {
     required String agentType,
     required String message,
     String? conversationId,
+    String? imageUrl,
+    String? pdfUrl,
     required String token,
   }) {
     final params = <String, String>{
@@ -19,6 +21,12 @@ class SseHandler {
     if (conversationId != null) {
       params['conversationId'] = conversationId;
     }
+    if (imageUrl != null && imageUrl.isNotEmpty) {
+      params['imageUrl'] = imageUrl;
+    }
+    if (pdfUrl != null && pdfUrl.isNotEmpty) {
+      params['pdfUrl'] = pdfUrl;
+    }
     final query = params.entries
         .map((e) => '${e.key}=${Uri.encodeComponent(e.value)}')
         .join('&');