feat: dynamic logo from synced assets + SVG favicon

Logo handler now checks Hub-synced assets first, falling back to
embedded SVG. Added SVG favicon to layout and catchall templates.

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

controller/internal/web/templates/layout.html

@@ -5,6 +5,7 @@
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>{{.Title}} — Felhom.eu</title>
+    <link rel="icon" type="image/svg+xml" href="/static/felhom-logo.svg">
     <link rel="stylesheet" href="/static/style.css">
     <meta name="csrf-token" content="{{.CSRFToken}}">
     <script>