refactor(frontend): P0 API 层收口与 http 统一

- 统一 http.ts baseURL：get/post/download/upload 均走 resolveApiUrl
- agentUtils 下沉至 lib/agent-utils，API 层移除对 components 的依赖
- 扩展 metricsApi/snmpApi/prometheusProxyApi/zabbixProxyApi
- 扩展 pipelineApi/credentialApi 覆盖流水线与凭证场景
- 14 个组件/页面禁止直连 http，统一走 @/services/api

frontend/src/components/deploy/CredentialFormDialog.tsx

@@ -8,8 +8,7 @@ import { Label } from '@/components/ui/label';
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select';
 import { Plus, Key, Globe, Container } from 'lucide-react';
 import { toast } from 'sonner';
-import { deployApi } from '@/services/api';
-import http from '@/services/http';
+import { credentialApi, deployApi } from '@/services/api';
 
 interface Repo {
   id: number; name: string; url: string; credential_id: number | null;
@@ -48,7 +47,7 @@ export default function CredentialFormDialog({ open, onOpenChange, type, editId,
 
   const loadCredentials = async () => {
     try {
-      const res: Record<string, any> = await http.get('/credentials?page_size=100');
+      const res: Record<string, any> = await credentialApi.list({ page_size: 100 });
       setCredentials(res?.list || []);
     } catch { /* silent */ }
   };