feat: add Hugo blog with terminal-bus theme

Scaffold the bus.saillant.cc blog: Hugo site config, a hand-written
vendored theme (terminal-bus, zero deps), and the first post plus an
about page.

The theme is minimal on purpose: single baseof/home/page/section
layouts and one CSS file, styled as a terminal/hackerspace prompt
(green-on-dark, ASCII banner, monospace). No upstream theme pulled in,
per the no-blind-dependency policy.

Consumes journal entries later (Task 4); build output feeds deploy.sh
(Task 8). blog/public/ and blog/resources/ stay gitignored.

blog/themes/terminal-bus/layouts/section.html

@@ -0,0 +1,11 @@
+{{ define "main" }}
+<h1><span class="prompt">$</span> ls {{ .Section }}/</h1>
+<ul class="post-list">
+  {{ range .Pages }}
+  <li>
+    <span class="date">{{ .Date.Format "2006-01-02" }}</span>
+    <a href="{{ .RelPermalink }}">{{ .Title }}</a>
+  </li>
+  {{ end }}
+</ul>
+{{ end }}