Photo lightbox now centers images at any photo count

Fixed layout bug where large photo counts pushed the main image off-screen and hid navigation.

Bug Fixes

The lightbox container was expanding to fit its thumbnail filmstrip — at 100+ photos, this could exceed 5000 pixels wide, pushing the main image off-screen and making prev/next buttons inaccessible.

Now the container respects the dialog width and the filmstrip scrolls horizontally instead. Main image stays centered and navigation controls remain within reach.