Edit the watermark in place, rotate the frame photo, place a custom watermark

Watermark editing no longer covers the photo: the preview letterboxes the
image inside its fit rect while the deck is open, and the idle hint is gone.

The FRAME tab can rotate a library photo 90 degrees clockwise. Rotation
swaps the pixel dimensions instead of the frame, so the polaroid/wall window
keeps its aspect and every consumer (cover crop, watermark area, export) picks
up the new orientation from width()/height() with no extra layout branch. The
rotate surface is CPU-backed on purpose - a GPU snapshot loses its pixels
before the next frame and renders the photo black.

Custom watermark text can now be dragged anywhere on the photo, double-tapped
to re-edit, and is only baked into the file once ACCEPT is pressed; the export
engine takes the same position. It also gained COLOR/SIZE/FONT chips, with the
font list read from the OS via Skia's FontMgr so any installed family can be
used.

src/utils/skiaImage.ts

@@ -0,0 +1,27 @@
+import { Skia, type SkImage } from '@shopify/react-native-skia';
+
+// Turn a decoded image 90deg clockwise into a fresh SkImage. Used by the FRAME
+// tab so a library photo can go landscape <-> portrait before it enters a frame:
+// every consumer reads width()/height(), so the pixel-dimension swap carries the
+// new orientation through the polaroid window aspect, the cover crop and the
+// watermark areas without a single extra layout branch.
+// ponytail: offscreen surface, same fallback as exportEngine.createSurface; a
+// matrix-based draw would avoid the copy if this ever shows up in a profile.
+export function rotateSkImage90(image: SkImage | null): SkImage | null {
+  if (!image) return null;
+  const w = image.width();
+  const h = image.height();
+  if (!(w > 0 && h > 0)) return null;
+  // CPU-backed on purpose: a GPU (MakeOffscreen) snapshot keeps its pixels in a
+  // context texture that is gone by the time the <Canvas> draws a frame later —
+  // the preview then renders the photo completely black. Raster pixels survive
+  // the trip to the render thread.
+  const surface = Skia.Surface.Make(h, w);
+  if (!surface) return image; // keep the unrotated photo on allocation failure
+  const canvas = surface.getCanvas();
+  canvas.clear(Skia.Color('transparent'));
+  canvas.translate(h, 0);
+  canvas.rotate(90, 0, 0);
+  canvas.drawImage(image, 0, 0);
+  return surface.makeImageSnapshot() ?? image;
+}