feat(routing): add client picker to user rules (#6271)

* feat(routing): add client picker to user rules

Replace the free-text user criterion with a searchable multi-select backed by existing panel clients. Preserve saved values that no longer exist so editing legacy rules remains lossless.

* feat(routing): polish user picker states

Align the routing user selector with the inbound-tag multi-select, including search, clear, loading, empty, and error states. Localize the new copy across every supported locale and cover legacy saved users with a regression test.

* fix(routing): keep custom user identifiers

Use tags mode with comma tokenization so the user picker suggests panel clients without rejecting HTTP, Mixed, or raw-template identifiers. Restore the comma hint and cover custom entries with a regression test.

frontend/src/api/queries/useClientOptions.ts

@@ -0,0 +1,33 @@
+import { useQuery } from '@tanstack/react-query';
+import { z } from 'zod';
+
+import { HttpUtil } from '@/utils';
+import { parseMsg } from '@/utils/zodValidate';
+import { keys } from '@/api/queryKeys';
+import { ClientRecordSchema, type ClientRecord } from '@/schemas/client';
+
+const ClientRecordListSchema = z
+  .array(ClientRecordSchema)
+  .nullable()
+  .transform((value) => value ?? []);
+
+async function fetchClients(): Promise<ClientRecord[]> {
+  const msg = await HttpUtil.get('/panel/api/clients/list', undefined, { silent: true });
+  if (!msg?.success) throw new Error(msg?.msg || 'Failed to load clients');
+  const validated = parseMsg(msg, ClientRecordListSchema, 'clients/list');
+  return validated.obj ?? [];
+}
+
+export function useClientOptions(enabled = true) {
+  return useQuery({
+    queryKey: keys.clients.all(),
+    queryFn: fetchClients,
+    enabled,
+    staleTime: 30_000,
+    select: (clients) =>
+      clients
+        .map((client) => client.email.trim())
+        .filter(Boolean)
+        .sort((a, b) => a.localeCompare(b)),
+  });
+}