Add recently played tracking with shows and broadcasts

- sql/schema.sql: shows, broadcasts and played_tracks tables, seeded
  with the five shows
- cli/poll_icecast.php: cron-run poller that records broadcasts and
  tracks every 15 seconds while streaming; tracks are cleared ten
  minutes after a broadcast ends
- cli/set_show.php: queue the next show, or assign one to the live
  broadcast
- recently_played.php: track history rows for live.php, with album art
  and album title linking to Last.fm
- live.php: recently played list, show name in heading, and per-show
  header background
- includes/icecast.php: Icecast parsing, album art and Last.fm helpers
  shared by now_playing.php and the poller
- includes/db.php: use UTC for the database session

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

includes/db.php

@@ -26,5 +26,7 @@ function getDB(): PDO {
         PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
         PDO::ATTR_EMULATE_PREPARES   => false,
     ]);
+    // Store and compare all DATETIME values in UTC
+    $pdo->exec("SET time_zone = '+00:00'");
     return $pdo;
 }