feat(frontend): replace placeholder avatar with identicons

i don't actually know what the license on the kitten image is, and while
it's very unlikely, i don't want to get into legal trouble. it was only
ever supposed to be a temporary image, too.

identicons aren't the prettiest but at least they have a clear license
:3

Foxnouns.Frontend/src/lib/components/profile/ProfileHeader.svelte

@@ -22,6 +22,7 @@
 	<div class="row">
 		<div class="col-md-4 text-center">
 			<Avatar
+				name={"name" in profile ? profile.name : profile.username}
 				url={profile.avatar_url}
 				alt={$t("avatar-tooltip", { name })}
 				lazyLoad={lazyLoadAvatar}

Foxnouns.Frontend/src/lib/components/profile/user/MemberCard.svelte

@@ -36,6 +36,7 @@
 <div>
 	<a href="/@{username}/{member.name}">
 		<Avatar
+			name={member.name}
 			url={member.avatar_url}
 			lazyLoad
 			alt={$t("avatar-tooltip", { name: member.display_name })}