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/manifest.json

@@ -0,0 +1,30 @@
+{
+  "manifest_version": 3,
+  "name": "YTMusic Now Playing",
+  "version": "1.0.0",
+  "description": "Sends currently playing song info to a Now Playing server",
+  "browser_specific_settings": {
+    "gecko": {
+      "id": "ytmusic-now-playing@whats-that-music",
+      "strict_min_version": "109.0"
+    }
+  },
+  "permissions": ["storage"],
+  "host_permissions": [
+    "https://music.youtube.com/*",
+    "http://localhost:9095/*",
+    "http://localhost/*",
+    "http://127.0.0.1/*",
+    "https://*/*"
+  ],
+  "content_scripts": [
+    {
+      "matches": ["https://music.youtube.com/*"],
+      "js": ["content.js"],
+      "run_at": "document_idle"
+    }
+  ],
+  "action": {
+    "default_popup": "popup.html"
+  }
+}