Pinch/drag library photo inside polaroid & wall frame windows with export parity

The framed windows (polaroid card / wall frame opening) now take the same pinch + double-tap gestures as plain library, clamped so the photo keeps covering the mat opening, and the visible sub-rectangle is handed to the export engine so the file matches the preview.

Wall frame export also stopped crashing: on Android release an image asset resolves to a drawable *name* ('wallframe') and is flagged downloaded, so Asset.downloadAsync short-circuited and readAsStringAsync threw 'Unsupported scheme for location wallframe'. Clearing that state lets the native module copy the drawable into the cache.

App.tsx

@@ -748,6 +748,9 @@ export default function App() {
           {
             aspect: aspectRatio === 'full' ? undefined : aspectRatio,
             watermark: wmForExport(),
+            // Pinch/drag inside a polaroid card window or wall-frame opening:
+            // save the same crop the preview showed (null = centered 1x).
+            frameWindowZoom: viewfinderRef.current?.getFrameWindowZoom?.() ?? null,
           }
         );