refactor: extract navbar and footer into reusable handlebars partials

- Replace duplicated navbar markup across all HTML pages with {{> navbar }} partial
- Replace duplicated footer markup across all HTML pages with {{> footer }} partial
- Add TypeScript type definitions for vite-plugin-handlebars integration
- Update vite.config.ts to support handlebars partial compilation
- Update tsconfig.json to include handlebars type definitions
- Update nginx.conf for proper static file serving with partials
- Update translation files for de, pt, tr, vi, and zh-TW locales
- Reduce code duplication and improve maintainability across 13+ HTML pages
- Ensure consistent navbar and footer behavior across the entire application

public/locales/de/common.json

@@ -8,6 +8,10 @@
     "openMainMenu": "Hauptmenü öffnen",
     "language": "Sprache"
   },
+  "donation": {
+    "message": "Lieben Sie BentoPDF? Helfen Sie uns, es kostenlos und Open Source zu halten!",
+    "button": "Spenden"
+  },
   "hero": {
     "title": "Das",
     "pdfToolkit": "PDF-Toolkit",