style: refine admin & me UI — card forms, back arrows, avatar in admin sidebar, Empty component

- Replace ← text with icon-[ri--arrow-left-line] in admin and me layouts
- Add avatar + admin shield badge to admin sidebar header
- Wrap all admin edit forms in Card (bg-card/50 border-primary/20) with styled inputs
- Fix sm:pl-6 → lg:pl-6 so extra left padding only applies when sidebar is visible
- Update security form submit button to gradient style matching profile
- Remove "View Public Profile" button from me/profile
- Use shadcn-svelte Empty component for recordings empty state
- Install empty component via shadcn-svelte

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/frontend/src/routes/me/profile/+page.svelte

@@ -2,7 +2,7 @@
   import { _ } from "svelte-i18n";
   import { invalidateAll } from "$app/navigation";
   import { untrack } from "svelte";
-  import { getAssetUrl, isModel } from "$lib/api";
+  import { getAssetUrl } from "$lib/api";
   import { toast } from "svelte-sonner";
   import { updateProfile, uploadFile, removeFile } from "$lib/services";
   import { Button } from "$lib/components/ui/button";
@@ -129,18 +129,12 @@
 
 <Meta title={$_("me.settings.profile_title")} />
 
-<div class="py-3 sm:py-6 sm:pl-6">
-  <div class="flex items-center justify-between mb-6 px-3 sm:px-0">
+<div class="py-3 sm:py-6 lg:pl-6">
+  <div class="mb-6">
     <h1 class="text-2xl font-bold">{$_("me.settings.profile_title")}</h1>
-    {#if isModel(data.authStatus.user!)}
-      <Button href={`/models/${data.authStatus.user!.slug}`} variant="outline">
-        {$_("me.view_profile")}
-      </Button>
-    {/if}
   </div>
 
-  <div class="px-3 sm:px-0">
-    <Card class="bg-card/50 border-primary/20 max-w-2xl">
+  <Card class="bg-card/50 border-primary/20 max-w-2xl">
       <CardHeader>
         <CardTitle>{$_("me.settings.profile_title")}</CardTitle>
         <CardDescription>{$_("me.settings.profile_subtitle")}</CardDescription>
@@ -287,5 +281,4 @@
         </form>
       </CardContent>
     </Card>
-  </div>
 </div>