feat(api,frontend): add qr code login

frontend/src/lib/api/endpoints.ts

@@ -53,6 +53,14 @@ export function startLogin(phone: string): Promise<LoginState> {
   });
 }
 
+export function startQrLogin(): Promise<LoginState> {
+  return request<LoginState>("/accounts/login/qr", { method: "POST" });
+}
+
+export function pollQrLogin(loginId: string): Promise<LoginState> {
+  return request<LoginState>(`/accounts/login/${loginId}/qr`);
+}
+
 export function submitLoginCode(
   loginId: string,
   code: string