Mobile: cannot zoom into images in galleries and image overlays

[Laoujin]

Problem

On mobile/touch devices you can't zoom into images opened from any of our three image mechanisms. The fullscreen overlays fit the image to the viewport (max-width/height in vw/vh) but offer no way to pinch-zoom or pan, so fine detail (UI screenshots, small text) stays unreadable.

Needs to be verified on a real device, but by inspection none of the overlays support gesture zoom.

Affected mechanisms

1. Cover gallery (_includes/gallery.html, type: cover) → .pf-lightbox overlay. Image is max-width:92vw; max-height:88vh (_sass/_pirateflix.scss:804), no zoom/pan.
2. Inline gallery (_includes/gallery.html, type: inline) → thumbnails open in the shared .pf-imgzoom overlay (assets/js/image-zoom.js).
3. Post image include (_includes/post/image.html) → .pf-imgzoom overlay, image max-width:92vw; max-height:92vh (_sass/_pirateflix.scss:836).

Expected

Once an image is open fullscreen, a mobile user should be able to pinch-zoom and pan to inspect detail.

Notes / possible approaches

• Overlays are currently fit-to-viewport only; there's no touch-action/pan handling and pinch-zoom isn't available inside the fixed overlay.
• Options: allow native pinch-zoom within the overlay, or add explicit zoom/pan behaviour to image-zoom.js and the .pf-lightbox slides.
• Whatever is chosen should apply consistently across all three mechanisms since (2) and (3) share .pf-imgzoom.