feat: add per-gallery thumbnail scale setting (#172) (#251)

Add a thumbnailScale field (xs/sm/md/lg/xl) to gallery layout settings
that adjusts column counts for Grid, Masonry (columns mode), and Mosaic
layouts. Each scale maps to a column offset applied on top of the
layout's base columns, letting photographers control photo density.

- Add thumbnailScale to GalleryLayoutSettings type
- Apply scale offset in Grid, Masonry, and Mosaic layout components
- Add thumbnail scale dropdown to admin theme customizer
- Conditionally show dropdown only for applicable layouts
- Safelist dynamic grid-cols classes in Tailwind config
- Add i18n keys for EN, DE, PT, RU locales

Co-authored-by: Paul Nothaft <[email protected]>

frontend/tailwind.config.js

@@ -84,6 +84,13 @@ export default {
       },
     },
   },
+  safelist: [
+    // Dynamic grid-cols classes used by thumbnail scale offsets
+    ...Array.from({ length: 12 }, (_, i) => `grid-cols-${i + 1}`),
+    ...Array.from({ length: 12 }, (_, i) => `sm:grid-cols-${i + 1}`),
+    ...Array.from({ length: 12 }, (_, i) => `lg:grid-cols-${i + 1}`),
+    ...Array.from({ length: 12 }, (_, i) => `xl:grid-cols-${i + 1}`),
+  ],
   plugins: [],
 }