refactor: stop recording triggers file download instead of browser storage

Recording flow: click Stop → frames packed into .mjpeg blob → browser
download triggered immediately. No more IndexedDB or OPFS.

Playback: use 'Load Recording File' button to open a .mjpeg file.
Removed all storage dependencies — pure file-based, 100% reliable.

dist/index.html

@@ -5,8 +5,8 @@
     <link rel="icon" href="/favicon.ico">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>MJPEG Stream Viewer</title>
-    <script type="module" crossorigin src="/assets/index-2XEhnc0l.js"></script>
-    <link rel="stylesheet" crossorigin href="/assets/index-BTgh_FTp.css">
+    <script type="module" crossorigin src="/assets/index-CHMLXxlv.js"></script>
+    <link rel="stylesheet" crossorigin href="/assets/index-Deon0U_J.css">
   </head>
   <body>
     <div id="app"></div>