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>

package.json

@@ -28,5 +28,13 @@
   "engines": {
     "node": ">=18.0.0"
   },
-  "packageManager": "pnpm@9.15.0"
+  "packageManager": "pnpm@9.15.0",
+  "pnpm": {
+    "peerDependencyRules": {
+      "allowedVersions": {
+        "@mana-core/nestjs-integration>@nestjs/common": "^11.0.0",
+        "@mana-core/nestjs-integration>@nestjs/core": "^11.0.0"
+      }
+    }
+  }
 }