Add WATERMARK tab with custom draggable text; hide FRAME in camera; fix double-dark after highlight capture

src/utils/nativeExport.ts

@@ -32,6 +32,11 @@ export interface NativeExportOptions {
   // Composition aspect-ratio crop ('full'/undefined = none). Native computes the
   // center-largest rect after decode because the pixel size is only known there.
   aspect?: AspectRatio;
+  // Custom text watermark overlay — position fractions of the photo area, same
+  // contract as ExportOptions.watermark. SHIPPED but NOT drawn yet: the Kotlin
+  // module renders geo captions but has no text-watermark draw (ponytail: add
+  // it when native parity with the Skia engine is completed).
+  watermark?: { text: string; x: number; y: number } | null;
 }
 
 // The Kotlin module reads plain absolute paths, not file:// URIs.