feat(settings): click own avatar in profile preview to view fullscreen

Lightbox was previously a file-private component inside AttachmentImage
(used for enlarging chat image attachments). Extracted to a standalone
components/Lightbox.tsx so other surfaces can reuse the same dialog
without duplicating Esc/backdrop/body-overflow plumbing.

In SettingsPage's profile live-preview, the round avatar overlapping the
banner is now wrapped in a transparent button that opens the Lightbox
with the full-resolution avatar URL on click. Cursor switches to
zoom-in. Disabled when the user only has the initial-letter placeholder
(nothing meaningful to enlarge). Native button chrome (border, padding,
button-face background) is reset to keep the avatar circle's appearance
unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop/src/components/AttachmentImage.tsx

@@ -3,7 +3,8 @@ import { useEffect, useState } from 'react';
 
 import { getCachedAttachment, putCachedAttachment } from '../lib/attachmentCache';
 import { supabase } from '../lib/supabase';
-import { AlertIcon, SpinnerIcon, XIcon } from './icons';
+import { AlertIcon, SpinnerIcon } from './icons';
+import { Lightbox } from './Lightbox';
 
 interface Props {
   handle: AttachmentHandle;
@@ -136,42 +137,5 @@ export function AttachmentImage({ handle }: Props) {
   );
 }
 
-function Lightbox({ url, onClose }: { url: string; onClose: () => void }) {
-  useEffect(() => {
-    function onKey(e: KeyboardEvent) {
-      if (e.key === 'Escape') onClose();
-    }
-    document.addEventListener('keydown', onKey);
-    const prevOverflow = document.body.style.overflow;
-    document.body.style.overflow = 'hidden';
-    return () => {
-      document.removeEventListener('keydown', onKey);
-      document.body.style.overflow = prevOverflow;
-    };
-  }, [onClose]);
-
-  return (
-    <div
-      role="dialog"
-      aria-modal="true"
-      aria-label="Bildansicht"
-      onClick={onClose}
-      className="fixed inset-0 z-50 flex items-center justify-center bg-ink-950/90 p-6 backdrop-blur-sm animate-fade-in"
-    >
-      <button
-        type="button"
-        onClick={onClose}
-        aria-label="Schließen"
-        className="absolute right-4 top-4 flex h-10 w-10 cursor-pointer items-center justify-center rounded-full border border-white/10 bg-ink-900/80 text-neutral-200 transition hover:bg-white/10 focus:outline-none focus-visible:ring-2 focus-visible:ring-brand-400/40"
-      >
-        <XIcon className="h-5 w-5" />
-      </button>
-      <img
-        src={url}
-        alt="attachment full"
-        onClick={(e) => e.stopPropagation()}
-        className="max-h-[92vh] max-w-[92vw] rounded-xl object-contain shadow-2xl"
-      />
-    </div>
-  );
-}
+// Lightbox extracted to ./Lightbox.tsx so the settings avatar preview and
+// any future surface can reuse the same dialog without duplication.