fix: apply QA fixes to correct build source (public/src/)

- BUG-055: Remove duplicate preconnect tags from homepage
- BUG-058: Add twitter:image meta tag to homepage
- BUG-060: Add og:title/description/url to sub-pages (impressum/privacy/terms/status)
- BUG-061: Already done in sitemap.xml
- BUG-067: Add skip-to-content link via nav partial + styles_base
- BUG-069: Footer already added to docs.html
- BUG-053: Minify app.js and status.js, update HTML refs

public/partials/_nav.html

@@ -1,3 +1,4 @@
+<a href="#main" class="skip-link">Skip to content</a>
 <nav aria-label="Main navigation">
   <div class="container">
     <a href="/" class="logo">⚡ Doc<span>Fast</span></a>

public/partials/_styles_base.html

@@ -36,4 +36,6 @@ footer .container { display: flex; justify-content: space-between; align-items:
 }
 
 .sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
+.skip-link { position: absolute; top: -100%; left: 16px; background: var(--accent); color: #0b0d11; padding: 8px 16px; border-radius: 0 0 8px 8px; font-weight: 600; font-size: 0.9rem; z-index: 200; transition: top 0.2s; text-decoration: none; }
+.skip-link:focus { top: 0; }
 </style>