feat(shared-auth-ui): redesign login page with animations and theme support

- Migrate icons from custom implementation to @manacore/shared-icons (phosphor-svelte)
- Add CSS media queries for dark/light mode (no more flash on reload)
- Add subtle entrance animations (logo fadeInScale, form fadeInUp, slider fadeIn)
- Redesign custom checkbox with CSS-only styling
- Remove isDark prop dependency, use prefers-color-scheme instead
- Update auth layout to allow full-page rendering

Also updates AppSlider component:
- Add staggered entrance animations for app cards
- Redesign modal with glassmorphism style
- Add theme-aware styling via CSS media queries
- Improve status badge design in modal
- Add close button in top-right corner

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/chat/apps/web/src/routes/(auth)/+layout.svelte

@@ -2,8 +2,4 @@
 	let { children } = $props();
 </script>
 
-<div class="min-h-screen flex items-center justify-center bg-gray-50 dark:bg-gray-900 px-4 py-12">
-	<div class="w-full max-w-md">
-		{@render children()}
-	</div>
-</div>
+{@render children()}