Harden accessibility: ARIA roles, semantic buttons, alt text, form labels

- Replace clickable divs with semantic <button> elements (NoteCard, SearchView)
- Add role="dialog", aria-modal, aria-labelledby on all modals (Login, Quote, Zap, Lightbox)
- Add role="presentation" on overlay backdrops (NoteCard menu, emoji pickers)
- Add aria-label to all icon-only buttons (close, nav arrows, context menu)
- Add aria-expanded to context menu toggle
- Add meaningful alt text to all 35+ images (avatars, covers, thumbnails, media)
- Add aria-label to form inputs (search, onboarding login)

src/components/profile/ProfileMediaGallery.tsx

@@ -70,7 +70,7 @@ export function ProfileMediaGallery({ notes, loading }: { notes: NDKEvent[]; loa
               >
                 <img
                   src={item.url}
-                  alt=""
+                  alt="Media content"
                   className="w-full h-full object-cover"
                   loading="lazy"
                   onError={(e) => { (e.target as HTMLImageElement).style.display = "none"; }}
@@ -88,7 +88,7 @@ export function ProfileMediaGallery({ notes, loading }: { notes: NDKEvent[]; loa
                 {item.thumbnailId ? (
                   <img
                     src={`https://img.youtube.com/vi/${item.thumbnailId}/mqdefault.jpg`}
-                    alt=""
+                    alt="Video thumbnail"
                     className="w-full h-full object-cover"
                     loading="lazy"
                   />

src/components/profile/ProfileView.tsx

@@ -28,7 +28,7 @@ function TopFollowerAvatar({ pubkey }: { pubkey: string }) {
       {profile?.picture ? (
         <img
           src={profile.picture}
-          alt=""
+          alt={`${name}'s avatar`}
           className="w-5 h-5 rounded-sm object-cover bg-bg-raised"
           onError={(e) => { (e.target as HTMLImageElement).style.display = "none"; }}
         />
@@ -218,7 +218,7 @@ export function ProfileView() {
                 )}
                 <img
                   src={profile.banner}
-                  alt=""
+                  alt={`${name}'s banner`}
                   className="w-full h-full object-cover object-[center_30%] cursor-pointer hover:opacity-90 transition-opacity"
                   onClick={() => setBannerLightbox(true)}
                   onLoad={() => setBannerLoaded(true)}
@@ -233,7 +233,7 @@ export function ProfileView() {
                 {avatar ? (
                   <img
                     src={avatar}
-                    alt=""
+                    alt={`${name}'s avatar`}
                     style={{ width: 64, height: 64 }}
                     className="rounded-sm object-cover bg-bg-raised"
                     onError={(e) => { (e.target as HTMLImageElement).style.display = "none"; }}