fix(login): show the Quick Connect code in an auto-dismissing sheet

The code was shown in a native Alert, which has no programmatic
dismiss: after another device authorized the code and polling logged
the user in, the alert stayed open on top of the app.

Replace it with an in-app bottom sheet that closes itself once the
session is authorized. Dismissing only hides the code - polling
continues so login still completes if the code is authorized
afterwards; polling stops when leaving the login screen (parity with
TVLogin). The code can be tapped to copy (expo-clipboard, probed via
requireOptionalNativeModule so builds without the native module just
no-op).

package.json

@@ -54,6 +54,7 @@
     "expo-brightness": "~56.0.5",
     "expo-build-properties": "~56.0.15",
     "expo-camera": "~56.0.7",
+    "expo-clipboard": "~56.0.4",
     "expo-constants": "~56.0.16",
     "expo-crypto": "~56.0.4",
     "expo-dev-client": "~56.0.16",