init: scaffold OPENBUREAU site with shibui-derived theme

- Hugo site for openbureau.ch (Deutsch, i18n-ready for EN/IT)
- Theme themes/openbureau/ = local copy of shibui, customized via
  site-level layouts and assets to keep the theme reference clean
- Editorial typography stack: Newsreader serif body, Space Grotesk
  display, Inter for listings, IBM Plex Mono for technical meta
- Content structure: library/ (Theorie, Büroführung, Software) with
  manifest and colophon at root; software is a library category, not
  a separate top-level
- Three views over one source: Journal (chronological home),
  Library (atlas grouped by section + tag cloud), single articles

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

themes/openbureau/static/favicon_io/browserconfig.xml

@@ -0,0 +1,2 @@
+<?xml version="1.0" encoding="utf-8"?>
+<browserconfig><msapplication><tile><square70x70logo src="/ms-icon-70x70.png"/><square150x150logo src="/ms-icon-150x150.png"/><square310x310logo src="/ms-icon-310x310.png"/><TileColor>#ffffff</TileColor></tile></msapplication></browserconfig>

themes/openbureau/static/favicon_io/manifest.json

@@ -0,0 +1,41 @@
+{
+ "name": "App",
+ "icons": [
+  {
+   "src": "\/android-icon-36x36.png",
+   "sizes": "36x36",
+   "type": "image\/png",
+   "density": "0.75"
+  },
+  {
+   "src": "\/android-icon-48x48.png",
+   "sizes": "48x48",
+   "type": "image\/png",
+   "density": "1.0"
+  },
+  {
+   "src": "\/android-icon-72x72.png",
+   "sizes": "72x72",
+   "type": "image\/png",
+   "density": "1.5"
+  },
+  {
+   "src": "\/android-icon-96x96.png",
+   "sizes": "96x96",
+   "type": "image\/png",
+   "density": "2.0"
+  },
+  {
+   "src": "\/android-icon-144x144.png",
+   "sizes": "144x144",
+   "type": "image\/png",
+   "density": "3.0"
+  },
+  {
+   "src": "\/android-icon-192x192.png",
+   "sizes": "192x192",
+   "type": "image\/png",
+   "density": "4.0"
+  }
+ ]
+}