feat(web): dark Gitea UI, systemd installer, WEB-UI docs (W7)

Restyles every template with a hand-written dark Gitea-style theme
(web/static/app.css, ~270 lines: badges, buttons, cards, focus rings,
prefers-reduced-motion) and completes the htmx polling wiring for all
four dashboard cards. Adds the repeatable setup-web-linux.sh installer
(idempotent: pip install '[web]' non-editable, render ci-web.service,
template [web]/[web.oidc] into config.toml, prompt for keyring secrets,
print Gitea OIDC registration steps, enable/restart the unit) plus
deploy/systemd/ci-web.service and docs/WEB-UI.md.

src/ci_orchestrator/web/templates/partials/audit.html

@@ -6,30 +6,40 @@
 <section class="card" id="audit-card">
   <h2>Audit log</h2>
   {% if entries %}
-  <table>
-    <thead>
-      <tr>
-        <th>Time</th>
-        <th>User</th>
-        <th>Action</th>
-        <th>Target</th>
-        <th>Result</th>
-        <th>Detail</th>
-      </tr>
-    </thead>
-    <tbody>
-      {% for e in entries %}
-      <tr class="{{ 'row-alert' if e.result == 'error' else '' }}">
-        <td>{{ e.ts }}</td>
-        <td>{{ e.user }}</td>
-        <td>{{ e.action }}</td>
-        <td><code>{{ e.target }}</code></td>
-        <td>{{ e.result }}</td>
-        <td>{{ e.detail }}</td>
-      </tr>
-      {% endfor %}
-    </tbody>
-  </table>
+  <div class="table-wrap">
+    <table>
+      <thead>
+        <tr>
+          <th>Time</th>
+          <th>User</th>
+          <th>Action</th>
+          <th>Target</th>
+          <th>Result</th>
+          <th>Detail</th>
+        </tr>
+      </thead>
+      <tbody>
+        {% for e in entries %}
+        <tr class="{{ 'row-alert' if e.result == 'error' else '' }}">
+          <td>{{ e.ts }}</td>
+          <td>{{ e.user }}</td>
+          <td>{{ e.action }}</td>
+          <td><code>{{ e.target }}</code></td>
+          <td>
+            {% if e.result == "ok" %}
+            <span class="badge badge-success">ok</span>
+            {% elif e.result == "error" %}
+            <span class="badge badge-danger">error</span>
+            {% else %}
+            <span class="badge badge-warn">{{ e.result }}</span>
+            {% endif %}
+          </td>
+          <td>{{ e.detail }}</td>
+        </tr>
+        {% endfor %}
+      </tbody>
+    </table>
+  </div>
   {% else %}
   <p>No audit entries yet.</p>
   {% endif %}