style: refine admin edit forms and fix mobile padding

- Remove back button from admin entity edit pages (sidebar handles navigation)
- Remove cancel button from video/article forms, make submit button full-width
- Show actual entity title + subtitle on video/article edit pages
- Remove asterisks from Title/Slug field labels in i18n
- Remove px-3 sm:px-0 from all admin list page headers/filters (fixes mobile padding)

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

packages/frontend/src/routes/admin/queues/+page.svelte

@@ -128,12 +128,12 @@
 <Meta title={$_("admin.queues.title")} description={null} />
 
 <div class="py-3 sm:py-6 lg:pl-6">
-  <div class="flex items-center justify-between mb-6 px-3 sm:px-0">
+  <div class="flex items-center justify-between mb-6">
     <h1 class="text-2xl font-bold">{$_("admin.queues.title")}</h1>
   </div>
 
   <!-- Queue cards -->
-  <div class="flex flex-wrap gap-3 mb-6 px-3 sm:px-0">
+  <div class="flex flex-wrap gap-3 mb-6">
     {#each queues as queue (queue.name)}
       {@const isSelected = selectedQueue === queue.name}
       <div
@@ -196,7 +196,7 @@
 
   {#if selectedQueue}
     <!-- Status filter tabs -->
-    <div class="flex gap-1 mb-4 px-3 sm:px-0 flex-wrap">
+    <div class="flex gap-1 mb-4 flex-wrap">
       {#each STATUS_FILTERS as f (f.value ?? "all")}
         <Button
           variant={selectedStatus === f.value ? "default" : "outline"}