fix: refresh camera device list after permission grant

useCameraDevices fetches once on mount. First-run flow grants the
camera permission after the viewfinder mounted, so the device list
stays empty until remount/restart and the UI shows 'Camera not
available on this device'. Poll Camera.getAvailableCameraDevices()
for up to 6s after permission is granted and prefer the found device.

src/components/Viewfinder.tsx

@@ -1,6 +1,6 @@
-import React, { useEffect } from 'react';
+import React, { useEffect, useState } from 'react';
 import { View, Text, StyleSheet, Dimensions, TouchableOpacity } from 'react-native';
-import { Camera, useCameraDevice, useSkiaFrameProcessor } from 'react-native-vision-camera';
+import { Camera, useCameraDevice, useSkiaFrameProcessor, type CameraDevice } from 'react-native-vision-camera';
 import { useSharedValue } from 'react-native-reanimated';
 import {
   Canvas,
@@ -55,7 +55,32 @@ export default function Viewfinder({
   onRequestCameraPermission,
   cameraRef,
 }: ViewfinderProps) {
-  const device = useCameraDevice('back');
+  const hookedDevice = useCameraDevice('back');
+  // VisionCamera fetches the device list once when this component mounts. When the
+  // camera permission is granted *after* mount (first-run flow: GRANT button, then
+  // OS dialog), that list stays empty until remount/restart, so the camera would
+  // report "not available". Poll the native list briefly after permission is
+  // granted and prefer a freshly found device.
+  const [grantedDevice, setGrantedDevice] = useState<CameraDevice | undefined>();
+  useEffect(() => {
+    if (!cameraPermissionGranted) return;
+    let stop = false;
+    const iv = setInterval(() => {
+      const back = Camera.getAvailableCameraDevices().find((d) => d.position === 'back');
+      if (back && !stop) {
+        setGrantedDevice(back);
+        clearInterval(iv);
+        clearTimeout(to);
+      }
+    }, 250);
+    const to = setTimeout(() => clearInterval(iv), 6000);
+    return () => {
+      stop = true;
+      clearInterval(iv);
+      clearTimeout(to);
+    };
+  }, [cameraPermissionGranted]);
+  const device = grantedDevice ?? hookedDevice;
   const skiaImage = useImage(libraryImageUri || '');
   const customFont = useFont(
     require('../../assets/CourierPrime-Regular.ttf'),