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-auth/tsconfig.json

@@ -1,18 +1,17 @@
 {
   "compilerOptions": {
-    "target": "ES2020",
+    "target": "ES2022",
     "module": "ESNext",
     "moduleResolution": "bundler",
-    "lib": ["ES2020", "DOM", "DOM.Iterable"],
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
     "strict": true,
     "esModuleInterop": true,
     "skipLibCheck": true,
     "forceConsistentCasingInFileNames": true,
-    "declaration": true,
-    "declarationMap": true,
-    "outDir": "./dist",
-    "rootDir": "./src"
+    "isolatedModules": true,
+    "verbatimModuleSyntax": true,
+    "noEmit": true
   },
   "include": ["src/**/*"],
-  "exclude": ["node_modules", "dist"]
+  "exclude": ["node_modules"]
 }