Add YouTube Music now-playing server, OBS overlay, and browser extension

Node.js server on port 9095 receives now-playing data via POST and broadcasts
to connected WebSocket clients. Includes a Firefox/Chrome extension that scrapes
YouTube Music's player bar every 3s, an OBS-ready transparent overlay with
animated equalizer bars, and an image proxy to bypass CDN restrictions in OBS.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

extension/popup.html

@@ -0,0 +1,73 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <style>
+    * { box-sizing: border-box; margin: 0; padding: 0; }
+    body {
+      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
+      width: 320px;
+      padding: 16px;
+      background: #1a1a2e;
+      color: #e0e0e0;
+    }
+    h1 {
+      font-size: 14px;
+      font-weight: 600;
+      margin-bottom: 12px;
+      color: #ff4e45;
+    }
+    label {
+      display: block;
+      font-size: 12px;
+      margin-bottom: 4px;
+      color: #aaa;
+    }
+    input[type="text"] {
+      width: 100%;
+      padding: 8px 10px;
+      font-size: 13px;
+      border: 1px solid #333;
+      border-radius: 4px;
+      background: #16213e;
+      color: #e0e0e0;
+      outline: none;
+    }
+    input[type="text"]:focus {
+      border-color: #ff4e45;
+    }
+    button {
+      margin-top: 10px;
+      width: 100%;
+      padding: 8px;
+      font-size: 13px;
+      font-weight: 600;
+      border: none;
+      border-radius: 4px;
+      background: #ff4e45;
+      color: #fff;
+      cursor: pointer;
+    }
+    button:hover {
+      background: #e0433b;
+    }
+    #status {
+      margin-top: 10px;
+      font-size: 12px;
+      text-align: center;
+      min-height: 16px;
+    }
+    .status-ok { color: #4caf50; }
+    .status-err { color: #f44336; }
+    .status-info { color: #aaa; }
+  </style>
+</head>
+<body>
+  <h1>YTMusic Now Playing</h1>
+  <label for="serverUrl">Server URL</label>
+  <input type="text" id="serverUrl" placeholder="http://localhost:9095">
+  <button id="save">Save</button>
+  <div id="status" class="status-info"></div>
+  <script src="popup.js"></script>
+</body>
+</html>