feat(mobile): allow rear camera recordings

Closes #211

js/mobile/src/features/compose/VideoRecordingOverlay.tsx

@@ -1,6 +1,7 @@
 import { useEffect, useRef, useState } from "react";
 import { Platform, Pressable, StyleSheet, Text, View } from "react-native";
-import { CameraView } from "expo-camera";
+import { CameraView, type CameraType } from "expo-camera";
+import { SwitchCamera } from "lucide-react-native";
 import { logError } from "@/lib/errors";
 import {
   acquireRecordingAudioSession,
@@ -23,6 +24,7 @@ export function VideoRecordingOverlay({
   const [cameraReady, setCameraReady] = useState(false);
   const [recording, setRecording] = useState(false);
   const [elapsedMs, setElapsedMs] = useState(0);
+  const [facing, setFacing] = useState<CameraType>("front");
   const startedAtRef = useRef<number | null>(null);
   const cancelledRef = useRef(false);
 
@@ -105,7 +107,7 @@ export function VideoRecordingOverlay({
       <CameraView
         ref={cameraRef}
         style={StyleSheet.absoluteFill}
-        facing="front"
+        facing={facing}
         videoQuality="480p"
         videoBitrate={VIDEO_BITRATE_BPS}
         mode="video"
@@ -113,6 +115,20 @@ export function VideoRecordingOverlay({
         onCameraReady={() => setCameraReady(true)}
       />
 
+      {!recording && cameraReady ? (
+        <View className="absolute top-0 right-0 pt-14 pr-5">
+          <Pressable
+            onPress={() =>
+              setFacing((f) => (f === "front" ? "back" : "front"))
+            }
+            accessibilityLabel="Flip camera"
+            className="h-11 w-11 items-center justify-center rounded-full bg-white/15"
+          >
+            <SwitchCamera color="white" size={22} strokeWidth={1.75} />
+          </Pressable>
+        </View>
+      ) : null}
+
       {recording ? (
         <View
           pointerEvents="none"