fix(photos): resolve upload category selection and improve feedback buttons (#77)

- Fix upload category selection by looking up category from database
  and saving category_id to photos table (was being ignored before)
- Use category slug for filename generation during upload
- Improve Like/Comment button visibility in CarouselGalleryLayout and
  PhotoLightbox with semi-transparent background and border styling

frontend/src/components/gallery/PhotoLightbox.tsx

@@ -456,7 +456,7 @@ export const PhotoLightbox: React.FC<PhotoLightboxProps> = ({
                 onClick={() => {
                   setShowFeedback(!showFeedback);
                 }}
-                className="relative p-2 bg-white/10 hover:bg-white/20 rounded-full transition-colors"
+                className="relative p-2 bg-black/40 hover:bg-black/60 rounded-full border border-white/40 transition-colors"
                 aria-label="Toggle feedback"
                 title={`Photo feedback${(currentPhoto.comment_count ?? 0) > 0 ? ` (${currentPhoto.comment_count ?? 0} comments)` : ''}`}
               >

frontend/src/components/gallery/layouts/CarouselGalleryLayout.tsx

@@ -164,7 +164,7 @@ export const CarouselGalleryLayout: React.FC<BaseGalleryLayoutProps> = ({
                     });
                   } catch (_) {}
                 }}
-                className={`hover:bg-white/20 ${likedIds.has(currentPhoto.id) ? 'text-red-400' : 'text-white'}`}
+                className={`bg-black/30 hover:bg-black/50 rounded-full border border-white/40 ${likedIds.has(currentPhoto.id) ? 'text-red-400' : 'text-white'}`}
                 title="Like photo"
                 aria-pressed={likedIds.has(currentPhoto.id)}
               >
@@ -176,7 +176,7 @@ export const CarouselGalleryLayout: React.FC<BaseGalleryLayoutProps> = ({
                 variant="ghost"
                 size="sm"
                 onClick={() => { onOpenPhotoWithFeedback?.(currentIndex); }}
-                className="text-white hover:bg-white/20"
+                className="text-white bg-black/30 hover:bg-black/50 rounded-full border border-white/40"
                 title="Comment"
                 aria-label="Comment on photo"
               >