fix: replace IndexedDB with Origin Private File System (OPFS)

OPFS (navigator.storage.getDirectory) provides direct filesystem
access scoped to the app's origin. Much more reliable than IndexedDB
for large blob storage — no transaction blocking, no connection issues.

Layout: recordings/{id}.frames (packed binary) + index.json (metadata)
Each recording stored as a single file write then close.

dist/index.html

@@ -5,7 +5,7 @@
     <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-B6qcBY8r.js"></script>
+    <script type="module" crossorigin src="/assets/index-2XEhnc0l.js"></script>
     <link rel="stylesheet" crossorigin href="/assets/index-BTgh_FTp.css">
   </head>
   <body>