Gallery: photos open lightbox, add project button, watermark our photos

Gallery flow:
- Album covers now open the photo lightbox directly (full album set), while
  the title/"Read the story" link opens the article. Previously the whole card
  linked to the article and photos were only at the bottom of it.
- Each album carries its full photo set in a hidden js-lightbox grid; added
  main.js support for [data-lightbox-target] cover triggers.
- Added the missing main.js include on the gallery page (its lightbox, mobile
  menu and language switcher never ran before).
- Lightbox gained an optional "Read the story ->" button (data-project-url /
  data-project-label) shown only for gallery albums.

Watermark:
- Baked a subtle "(c) msosorg.com" watermark (bottom-right, sized per image)
  into 114 of our own event/community photos. Stock/partner/logo/icon images
  excluded. Clean originals backed up to images/_originals/ (git-ignored); the
  script always re-derives from them so re-runs never stack.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -2,3 +2,4 @@
 images/original/
 .playwright-mcp/
 code_export.txt
+images/_originals/