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/layouts/_default/list.html

@@ -0,0 +1,24 @@
+{{ define "main" }}
+    {{ .Content }}
+    <div class="time-list">
+        <ul>
+            {{ range .Pages }}
+            <li class="list-item">
+                {{ if .Params.image }}
+                <div class="list-image">
+                    <img src="{{ .Params.image }}" alt="{{ .LinkTitle }}">
+                </div>
+                {{ end }}
+                <div class="list-title-row">
+                    <div class="list-title">
+                        <a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a>
+                    </div>
+                    <div class="list-meta">
+                        {{ partial "date.html" .Date }}
+                    </div>
+                </div>
+            </li>
+            {{ end }}
+        </ul>
+    </div>
+{{ end }}