fix: reset TokenPocket request state on expired/failed poll

Clear tpRequest when a TokenPocket login expires or fails so the mobile UI
returns to the initial state instead of showing a stuck waiting spinner
alongside the error.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/wallet/WalletLoginModal.tsx

@@ -97,6 +97,7 @@ export function WalletLoginModal() {
         }
         if (result.status === "expired" || result.status === "failed") {
           setState("idle");
+          setTpRequest(null);
           setError(result.error || t("walletTpExpired"));
         }
       } catch (err) {