fix(access-logs): 修复概览域名筛选参数 hosts[] 被 Gin 忽略

Axios 默认序列化为 hosts[]=，Gin QueryArray("hosts") 读不到导致筛选失效；
后端兼容 hosts/hosts[]，前端改为重复键序列化。

frontend/lib/services/core/api-client.ts

@@ -28,6 +28,10 @@ const apiClient = axios.create({
   withCredentials: apiConfig.withCredentials,
   // Fail fast on slash redirect loops between Next dev proxy and Gin legacy routes.
   maxRedirects: 5,
+  // Gin QueryArray("hosts") expects hosts=a&hosts=b, not hosts[]=a.
+  paramsSerializer: {
+    indexes: null,
+  },
   headers: {
     'Content-Type': 'application/json',
   },

frontend/lib/services/core/search-params.ts

@@ -0,0 +1,22 @@
+/**
+ * Serialize query params for Gin-compatible repeated array keys.
+ * Axios default uses hosts[]= which Gin QueryArray("hosts") ignores.
+ */
+export function serializeSearchParams(
+  params?: Record<string, unknown>,
+): string {
+  if (!params) return '';
+  const search = new URLSearchParams();
+  for (const [key, value] of Object.entries(params)) {
+    if (value === undefined || value === null || value === '') continue;
+    if (Array.isArray(value)) {
+      for (const item of value) {
+        if (item === undefined || item === null || item === '') continue;
+        search.append(key, String(item));
+      }
+      continue;
+    }
+    search.append(key, String(value));
+  }
+  return search.toString();
+}