fix(web): 修复生产环境 API 不可用误报

apps/web/lib/api.ts

@@ -1,4 +1,14 @@
-const API_BASE = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001/api/v1';
+type ApiEnv = {
+  NEXT_PUBLIC_API_URL?: string;
+  NODE_ENV?: string;
+};
+
+export function resolveApiBase(env: ApiEnv = process.env) {
+  const fallback = env.NODE_ENV === 'production' ? '/api/v1' : 'http://localhost:3001/api/v1';
+  return (env.NEXT_PUBLIC_API_URL || fallback).replace(/\/$/, '');
+}
+
+const API_BASE = resolveApiBase();
 
 let apiAvailable: boolean | null = null;
 let probePromise: Promise<boolean> | null = null;
@@ -23,17 +33,19 @@ export class ApiRequestError extends Error {
 }
 
 async function checkApi(): Promise<boolean> {
-  if (apiAvailable !== null) return apiAvailable;
+  if (apiAvailable === true) return true;
   if (probePromise) return probePromise;
   probePromise = (async () => {
     try {
       // 探测一个不依赖数据库的端点（/config/ai 总是返回 200，只要 NestJS 起来了）
       const res = await fetch(`${API_BASE}/config/ai`, { method: 'GET', signal: AbortSignal.timeout(1500) });
-      apiAvailable = res.ok;
+      apiAvailable = res.ok ? true : null;
     } catch {
-      apiAvailable = false;
+      apiAvailable = null;
+    } finally {
+      probePromise = null;
     }
-    return apiAvailable;
+    return apiAvailable === true;
   })();
   return probePromise;
 }
@@ -45,7 +57,10 @@ async function request<T>(path: string, options?: RequestInit): Promise<T> {
     headers: { 'Content-Type': 'application/json', ...options?.headers },
     ...options,
   }).catch(() => null);
-  if (!res) throw new Error('API 不可用');
+  if (!res) {
+    apiAvailable = null;
+    throw new Error('API 不可用');
+  }
   if (!res.ok) {
     const error = await res.json().catch(() => ({}));
     throw new ApiRequestError(res.status, error);
@@ -83,3 +98,8 @@ export const api = {
     }
   },
 };
+
+export function __resetApiAvailabilityForTests() {
+  apiAvailable = null;
+  probePromise = null;
+}