feat(studio): two fingers on the stage are the phone's own zoom, for aiming FIX and HEAL

docker/frontend/src/styles/app.css

@@ -552,7 +552,12 @@ button.hint:disabled { cursor: default; }
    rather than riding on the sentence above it. The click on this button must
    not also open the file dialog the dropzone itself listens for. */
 .dropzone .btn { margin-top: 14px; }
-.canvas-wrap { position: relative; display: flex; align-items: center; justify-content: center; min-height: 0; flex: 1 1 auto; width: 100%; overflow: hidden; }
+/* `touch-action: none` because the two fingers are the stage's own gesture: the
+   browser would otherwise take a pinch on the photo for its own page zoom, cancel
+   the pointers under it, and the photo would never be the thing that grew. The
+   layers over the photo — the brush's, the masks' — already say the same; this is
+   the photo itself, and the space around it. */
+.canvas-wrap { position: relative; display: flex; align-items: center; justify-content: center; min-height: 0; flex: 1 1 auto; width: 100%; overflow: hidden; touch-action: none; }
 .canvas-wrap img { max-width: 100%; max-height: 100%; object-fit: contain; border-radius: var(--radius-sm); box-shadow: var(--shadow); }
 /* Crop editor: the layer is the photo's own box, the rect is the framing and
    its shadow is what shades the part being cut away. */