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/lib/components/logo/logo.svelte

@@ -2,6 +2,4 @@
   import SexyIcon from "../icon/icon.svelte";
 </script>
 
-<div class="relative">
-  <SexyIcon class="w-12 h-12" />
-</div>
+<SexyIcon class="w-12 h-12" />