fix(live-state): eliminate flash on poll by switching to innerHTML swap

outerHTML removes and re-inserts the section on each tick, causing a
blank frame. Keeping the <section> as a stable DOM container and
swapping only innerHTML means avatars and text update in-place without
any teardown/reconstruct cycle.

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

l4d2web/templates/_live_state.html

@@ -1,7 +1,3 @@
-<section class="panel live-state"
-         hx-get="/servers/{{ server.id }}/live-state"
-         hx-trigger="every {{ poll_seconds }}s"
-         hx-swap="outerHTML">
 <h2 class="section-title">Live state</h2>
 {% if not snapshot or not snapshot_fresh %}
   <p class="muted">No data — server is not currently reporting.</p>
@@ -62,4 +58,3 @@
     {% endfor %}
   </ul>
 {% endif %}
-</section>

l4d2web/templates/server_detail.html

@@ -22,7 +22,7 @@
   <section class="panel live-state"
            hx-get="/servers/{{ server.id }}/live-state"
            hx-trigger="load, every 5s"
-           hx-swap="outerHTML">
+           hx-swap="innerHTML">
   </section>
 
   <h2 class="section-title">Files</h2>