Add player functionality with HLS support and API integration

- Implemented a new Player class in player.js to handle audio playback, including HLS support using hls.js.
- Created a shared API module in api.js for making HTTP requests with proper error handling.
- Added DOM utility functions in dom.js for creating and clearing elements.
- Introduced WebSocket connection handling in ws.js for real-time updates.
- Developed a comprehensive CSS stylesheet for styling the application, including a high-contrast theme.

server/streams/checker.js

@@ -0,0 +1,25 @@
+import cron from 'node-cron';
+import { getDb } from '../db/index.js';
+import { probeStream } from './probe.js';
+
+const probe = probeStream;
+
+export async function runHealthCheck() {
+  const db = getDb();
+  const streams = db.prepare('SELECT id, url FROM streams').all();
+  const update = db.prepare(
+    "UPDATE streams SET last_status = ?, last_checked_at = datetime('now') WHERE id = ?"
+  );
+  for (const s of streams) {
+    const status = await probe(s.url);
+    update.run(status, s.id);
+  }
+  return streams.length;
+}
+
+export function scheduleHealthCheck(expr) {
+  if (!expr) return null;
+  return cron.schedule(expr, () => {
+    runHealthCheck().catch((err) => console.error('[health]', err));
+  });
+}