Add optional episode titles to queued and live broadcasts

Store an episode_title on each broadcast, settable from the dashboard
or with set_show.php --title=, and show it under the show name on
index.php and under the heading on live.php.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

index.php

@@ -119,6 +119,9 @@ if ($show) {
 <?php endif; ?>
 <?php endif; ?>
 							<h3><?= htmlspecialchars($show['name'], ENT_QUOTES, 'UTF-8') ?></h3>
+<?php if ($show['episode_title']): ?>
+							<p class="episode-title"><em><?= htmlspecialchars($show['episode_title'], ENT_QUOTES, 'UTF-8') ?></em></p>
+<?php endif; ?>
 <?php if ($show['started_at']): ?>
 							<p><strong><a href="live.php">Broadcasting Live</a></strong></p>
 <?php elseif ($when): ?>