Add Apps page with local icons, favicon, and React Router navigation

- Move app links to dedicated /apps page with grouped icon tiles
- Download all icons locally to public/icons/ (no CDN dependency)
- Add favicon and replace header logo-mark with custom icon
- Fix icon names: synology, termix, docsight-light, dbgate (png)
- Add nav tabs in header for Dashboard/Apps routing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

index.html

@@ -4,6 +4,7 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>syco.me — Dashboard</title>
+    <link rel="icon" type="image/png" href="/icons/favicon.png" />
     <link rel="preconnect" href="https://fonts.googleapis.com" />
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
     <link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@300;400;500;600&family=Syne:wght@400;600;700;800&display=swap" rel="stylesheet" />