feat(auto-reply): 接入万川平台模型配置 + 各模型独立网关回退

万川平台对接
- 新增 wanchuan_proxy.go：WanchuanLogin/WanchuanGetModel 代理登录与按 code 拉取模型，
  日志对 password/token/apiKey 打码（含 encryptedConfig 二次解析）
- 新增 PlatformConfig（baseUrl/username/password）及 Get/SavePlatformConfig 持久化
- 前端万川卡片：登录→拉取 chat/vision/embedding/rerank/voice→回填 form 并保存→必要时重建向量索引

各模型独立网关（url+key），留空回退聊天网关
- RetrievalConfig 新增 embeddingBaseUrl/embeddingApiKey、rerankBaseUrl/rerankApiKey
- embeddingRequestConfig/rerankRequestConfig：优先独立网关，未配置回退 AI.BaseURL/APIKey
- vision/audio 同模式：非 DashScope 网关下视觉/语音模型留空时不再锁死或强写 DashScope，
  运行期由 fallbackString(VisionModel, Model) 动态复用聊天模型

陈旧向量空间防护
- loadEmbeddingIndex 检测磁盘索引与当前 embedding 模型/维度不一致时清空向量、回退关键词检索，
  并提示重建（embeddingIndexStaleReason，兼容旧版无模型名索引）

UI 状态修复
- 登录拉模型期间统一置全局 busy，禁用闸门收敛为 busy（与刷新联系人等按钮同范式），
  platformBusy 仅保留用于按钮「处理中…」文案，杜绝并发读写 form 与反向可点洞

其他
- 删除遗留 helper/auto_reply_ai.go.bak
- 补充 config/helper 单元测试（视觉回退分支、陈旧索引判定）

frontend/wailsjs/go/main/App.d.ts

@@ -46,6 +46,8 @@ export function GetKingdeeMonitorStatus():Promise<any>;
 
 export function GetPendingAfterSalesArchiveSummary():Promise<any>;
 
+export function GetPlatformConfig():Promise<any>;
+
 export function GetSystemMemoryUsage():Promise<number>;
 
 export function GetWxWorkAccountList():Promise<any>;
@@ -90,6 +92,8 @@ export function SaveIssue(arg1:main.AfterSalesIssue):Promise<boolean|string>;
 
 export function SaveKingdeeMonitorConfig(arg1:string):Promise<boolean|string>;
 
+export function SavePlatformConfig(arg1:string):Promise<boolean|string>;
+
 export function SendWxWorkData(arg1:string,arg2:string):Promise<boolean>;
 
 export function SetAutoCollectTask(arg1:boolean):Promise<boolean|string>;
@@ -113,3 +117,7 @@ export function TestKingdeeMonitorConnection(arg1:string):Promise<any>;
 export function TriggerManualCollect(arg1:string):Promise<boolean|string>;
 
 export function UpdateAfterSalesKnowledgeCase(arg1:string,arg2:string):Promise<any>;
+
+export function WanchuanGetModel(arg1:string,arg2:string,arg3:string):Promise<string>;
+
+export function WanchuanLogin(arg1:string,arg2:string,arg3:string):Promise<string>;

frontend/wailsjs/go/main/App.js

@@ -90,6 +90,10 @@ export function GetPendingAfterSalesArchiveSummary() {
   return window['go']['main']['App']['GetPendingAfterSalesArchiveSummary']();
 }
 
+export function GetPlatformConfig() {
+  return window['go']['main']['App']['GetPlatformConfig']();
+}
+
 export function GetSystemMemoryUsage() {
   return window['go']['main']['App']['GetSystemMemoryUsage']();
 }
@@ -178,6 +182,10 @@ export function SaveKingdeeMonitorConfig(arg1) {
   return window['go']['main']['App']['SaveKingdeeMonitorConfig'](arg1);
 }
 
+export function SavePlatformConfig(arg1) {
+  return window['go']['main']['App']['SavePlatformConfig'](arg1);
+}
+
 export function SendWxWorkData(arg1, arg2) {
   return window['go']['main']['App']['SendWxWorkData'](arg1, arg2);
 }
@@ -225,3 +233,11 @@ export function TriggerManualCollect(arg1) {
 export function UpdateAfterSalesKnowledgeCase(arg1, arg2) {
   return window['go']['main']['App']['UpdateAfterSalesKnowledgeCase'](arg1, arg2);
 }
+
+export function WanchuanGetModel(arg1, arg2, arg3) {
+  return window['go']['main']['App']['WanchuanGetModel'](arg1, arg2, arg3);
+}
+
+export function WanchuanLogin(arg1, arg2, arg3) {
+  return window['go']['main']['App']['WanchuanLogin'](arg1, arg2, arg3);
+}