feat: add React Query hooks for email connector API

ui/src/api/email-connector-hooks.ts

@@ -0,0 +1,70 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { api } from './client';
+
+export interface EmailConnectorResponse {
+  connectorId: string;
+  factoryId: string;
+  host: string;
+  port: number;
+  username: string;
+  fromEmail: string;
+  registrationEnabled: boolean;
+}
+
+export interface SmtpConfigRequest {
+  host: string;
+  port: number;
+  username: string;
+  password: string;
+  fromEmail: string;
+  registrationEnabled?: boolean;
+}
+
+export interface TestEmailResult {
+  status: string;
+  message: string;
+}
+
+export function useEmailConnector() {
+  return useQuery<EmailConnectorResponse | null>({
+    queryKey: ['vendor', 'email-connector'],
+    queryFn: async () => {
+      try {
+        return await api.get<EmailConnectorResponse>('/vendor/email-connector');
+      } catch (e) {
+        if (e instanceof Error && e.message.includes('404')) return null;
+        throw e;
+      }
+    },
+  });
+}
+
+export function useSaveEmailConnector() {
+  const qc = useQueryClient();
+  return useMutation<EmailConnectorResponse, Error, SmtpConfigRequest>({
+    mutationFn: (config) => api.post('/vendor/email-connector', config),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['vendor', 'email-connector'] }),
+  });
+}
+
+export function useDeleteEmailConnector() {
+  const qc = useQueryClient();
+  return useMutation<void, Error, void>({
+    mutationFn: () => api.delete('/vendor/email-connector'),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['vendor', 'email-connector'] }),
+  });
+}
+
+export function useTestEmailConnector() {
+  return useMutation<TestEmailResult, Error, string>({
+    mutationFn: (to) => api.post('/vendor/email-connector/test', { to }),
+  });
+}
+
+export function useToggleRegistration() {
+  const qc = useQueryClient();
+  return useMutation<void, Error, boolean>({
+    mutationFn: (enabled) => api.post('/vendor/email-connector/registration', { enabled }),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['vendor', 'email-connector'] }),
+  });
+}