Let the GPS watermark be placed, sized and hung landscape

Three WATERMARK/FRAME behaviours that share the stamp geometry:

* GPS mark: drag it anywhere on the frame/photo area and pinch it bigger or
  smaller. The 0..1 anchor plus the size multiplier ride along in the export
  options, so a framed file (whose canvas IS the card/frame) burns the mark in
  at exactly the fraction the preview showed.
* The photo's own pinch zoom stays available while the WATERMARK editor is
  closed, so a two-finger zoom is never swallowed by the mark while its panel
  is open.
* WALL FRAME gains a WALL PORTRAIT / WALL LANDSCAPE chip: the artwork hangs
  in its own 4000x3117 orientation instead of the default 90-degree rotation.

src/types/index.ts

@@ -97,3 +97,13 @@ export interface CustomWatermark {
   size?: number; // multiplier on the base 3.2%-of-width text size
   font?: string | null; // OS font family; null/absent = bundled font
 }
+
+// GPS watermark placement (WATERMARK tab drag + pinch): x/y are 0..1 fractions
+// of the SAME area the custom mark uses (frame card / photo rect / screen), and
+// the anchor is the top-left corner of the two-line block. size multiplies the
+// base 3.2%-of-width size. Defaults reproduce the old fixed top-left look.
+export interface GpsWatermark {
+  x: number;
+  y: number;
+  size: number;
+}