refactor: UX and styling improvements across frontend

- Fix login spinner (isLoading never set to true before await)
- Extract PageHero component, replace copy-pasted hero sections on videos/models/tags pages
- Replace inline plasma blobs with SexyBackground on videos/models/tags pages
- Make video/model/tag cards fully clickable (wrap in <a>), remove redundant Watch/View Profile buttons
- Convert inner overlay anchors to divs to avoid nested <a> elements
- Fix home page model avatar preset: mini → thumbnail (correct size for 96px display)
- Reduce home hero height: min-h-screen → min-h-[70vh]
- Remove dead hideName prop from Logo, simplify component
- Add brand name to mobile flyout panel header with gradient styling
- Remove dead _relatedVideos array, isBookmarked state, _handleBookmark from video detail page
- Clean up commented-out code blocks in video detail and models pages
- Note: tag card inner tag links converted to spans to avoid nested anchors

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

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

@@ -12,7 +12,7 @@
 <Meta title={$_("home.hero.title")} description={$_("home.hero.description")} />
 
 <!-- Hero Section -->
-<section class="relative min-h-screen flex items-center justify-center overflow-hidden">
+<section class="relative min-h-[70vh] flex items-center justify-center overflow-hidden">
   <!-- Background Gradient -->
   <div class="absolute inset-0 bg-gradient-to-br from-primary/20 via-accent/10 to-background"></div>
 
@@ -77,7 +77,7 @@
           <CardContent class="p-6 text-center">
             <div class="relative mb-4">
               <img
-                src={getAssetUrl(model.avatar, "mini")}
+                src={getAssetUrl(model.avatar, "thumbnail")}
                 alt={model.artist_name}
                 class="w-24 h-24 rounded-full mx-auto object-cover ring-4 ring-primary/20 group-hover:ring-primary/40 transition-all"
               />