feat: add i18n localization with language switcher to all web apps

- Add svelte-i18n configuration with SSR support to all web apps
- Create LanguageSelector component for each app with brand colors
- Add German and English locale files
- Integrate language switcher into login pages via headerControls snippet
- Fix Tailwind v4 @source directives for shared package scanning
- Update AppSlider styling to match login container design

Apps updated:
- Memoro (gold #f8d62b)
- Märchenzauber (pink #FF6B9D)
- ManaDeck (purple #8b5cf6)
- ManaCore (indigo #6366f1)

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

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

packages/shared-subscription-ui/src/PackageCard.svelte

@@ -42,6 +42,7 @@
 	let isHovered = $state(false);
 </script>
 
+<!-- svelte-ignore a11y_no_static_element_interactions -->
 <div
 	class="relative rounded-xl p-4 transition-all duration-200 bg-content border hover:-translate-y-0.5 hover:shadow-lg"
 	class:border-mana={pkg.popular}

packages/shared-subscription-ui/src/SubscriptionCard.svelte

@@ -57,6 +57,7 @@
 	let isHovered = $state(false);
 </script>
 
+<!-- svelte-ignore a11y_no_static_element_interactions -->
 <div
 	class="relative rounded-xl p-4 transition-all duration-200 bg-content border hover:-translate-y-0.5 hover:shadow-lg"
 	class:border-2={isCurrentPlan}