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>

layouts/_partials/footer.html

@@ -0,0 +1,17 @@
+<div class="footer-grid">
+  <div class="footer-mark">OPENBUREAU</div>
+  <nav class="footer-nav" aria-label="Footer">
+    <ul>
+      <li><a href="/manifest/">Manifest</a></li>
+      <li><a href="/colophon/">Colophon</a></li>
+      <li><a href="https://openstudio.kgva.ch">Forum ↗</a></li>
+      <li><a href="https://gitea.kgva.ch">Code ↗</a></li>
+      <li><a href="/index.xml">RSS</a></li>
+    </ul>
+  </nav>
+  <p class="footer-tagline">
+    Sammlung, Plattform, Praxis.<br>
+    Texte unter <a href="https://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA 4.0</a>.
+  </p>
+  <p class="footer-credit">© {{ now.Year }} · Karim Gabriele Varano</p>
+</div>