fix: use presigned S3 URLs for avatar images instead of /uploads/ paths

Avatar images were rendered via /uploads/ which doesn't exist since
the S3 migration. Now the server enriches profile responses with
avatarImageUrl (presigned S3 URL) and the frontend uses it directly.
Also fixed the public profile page at /users/:id.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/client/hooks/useProfile.ts

@@ -5,6 +5,7 @@ interface PublicProfile {
 	id: number;
 	displayName: string | null;
 	avatarUrl: string | null;
+	avatarImageUrl: string | null;
 	bio: string | null;
 	setups: { id: number; name: string; createdAt: string }[];
 }