refactor(templates): use timeago filter for job timestamps

Preserves the existing '-' placeholder for nullable started_at /
finished_at columns.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

l4d2web/l4d2web/templates/_job_table.html

@@ -19,8 +19,8 @@
       <td>{{ job.state }}</td>
       {% if show_user %}<td>{{ user.username if user else "system" }}</td>{% endif %}
       {% if show_server %}<td>{% if server %}<a href="/servers/{{ server.id }}">{{ server.name }}</a>{% else %}-{% endif %}</td>{% endif %}
-      <td>{{ job.created_at }}</td>
-      <td>{{ job.finished_at or "-" }}</td>
+      <td>{{ job.created_at | timeago }}</td>
+      <td>{% if job.finished_at %}{{ job.finished_at | timeago }}{% else %}-{% endif %}</td>
       {% if show_cancel %}
       <td>
         {% if job.state in ["queued", "running"] %}

l4d2web/l4d2web/templates/job_detail.html

@@ -21,9 +21,9 @@
       <tr><th>State</th><td>{{ job.state }}</td></tr>
       <tr><th>User</th><td>{{ owner.username if owner else "system" }}</td></tr>
       <tr><th>Server</th><td>{% if server %}<a href="/servers/{{ server.id }}">{{ server.name }}</a>{% else %}-{% endif %}</td></tr>
-      <tr><th>Created</th><td>{{ job.created_at }}</td></tr>
-      <tr><th>Started</th><td>{{ job.started_at or "-" }}</td></tr>
-      <tr><th>Finished</th><td>{{ job.finished_at or "-" }}</td></tr>
+      <tr><th>Created</th><td>{{ job.created_at | timeago }}</td></tr>
+      <tr><th>Started</th><td>{% if job.started_at %}{{ job.started_at | timeago }}{% else %}-{% endif %}</td></tr>
+      <tr><th>Finished</th><td>{% if job.finished_at %}{{ job.finished_at | timeago }}{% else %}-{% endif %}</td></tr>
       <tr><th>Exit code</th><td>{{ job.exit_code if job.exit_code is not none else "-" }}</td></tr>
     </tbody>
   </table>