Add database connection helper and live now-playing page

- includes/db.php: getDB() returns a shared PDO connection to MariaDB
- config/db_credentials.example.php: credentials template; the real
  db_credentials.php is gitignored and deployed separately via SFTP
- live.php: page for active broadcasts, with the player on the left
  and a placeholder Recently Played table on the right

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

includes/db.php

@@ -0,0 +1,30 @@
+<?php
+// Shared database connection. Include this file and call getDB() to get a PDO handle.
+
+if (basename($_SERVER['SCRIPT_FILENAME'] ?? '') === basename(__FILE__)) {
+    http_response_code(403);
+    exit;
+}
+
+function getDB(): PDO {
+    static $pdo = null;
+    if ($pdo !== null) return $pdo;
+
+    $credentialsFile = __DIR__ . '/../config/db_credentials.php';
+    if (!is_readable($credentialsFile)) {
+        throw new RuntimeException('Database credentials file is missing.');
+    }
+    $cfg = require $credentialsFile;
+
+    $dsn = sprintf(
+        'mysql:host=%s;port=%d;dbname=%s;charset=%s',
+        $cfg['host'], $cfg['port'], $cfg['database'], $cfg['charset']
+    );
+
+    $pdo = new PDO($dsn, $cfg['username'], $cfg['password'], [
+        PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
+        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+        PDO::ATTR_EMULATE_PREPARES   => false,
+    ]);
+    return $pdo;
+}