Add managed catalog sync and player UX improvements

public/api/managed-stations.php

@@ -0,0 +1,42 @@
+<?php
+/**
+ * Managed catalog API endpoint.
+ * Served at /api/managed-stations.json via .htaccess rewrite.
+ * Returns the same JSON envelope as the Node backend: { schemaVersion, updatedAt, stations }.
+ */
+
+header('Content-Type: application/json; charset=utf-8');
+header('Cache-Control: no-cache');
+
+$catalogPath = __DIR__ . '/../stations.json';
+
+if (!is_file($catalogPath)) {
+    http_response_code(404);
+    echo json_encode(['error' => 'Catalog not found']);
+    exit;
+}
+
+$raw = file_get_contents($catalogPath);
+if ($raw === false) {
+    http_response_code(500);
+    echo json_encode(['error' => 'Failed to read catalog']);
+    exit;
+}
+
+$data = json_decode($raw, true);
+if ($data === null) {
+    http_response_code(500);
+    echo json_encode(['error' => 'Invalid catalog JSON']);
+    exit;
+}
+
+// Accept both plain array and already-enveloped format
+$stations = isset($data['stations']) ? $data['stations'] : $data;
+
+$envelope = [
+    'schemaVersion' => 1,
+    'updatedAt'     => date('c', filemtime($catalogPath)),
+    'stations'      => $stations,
+];
+
+echo json_encode($envelope, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);