Hub: add SW cleanup on load; add self-unregistering sw.js to kill stale Astro SW

hub/index.html

@@ -4,6 +4,16 @@
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>Bincio</title>
+  <script>
+    if ('serviceWorker' in navigator) {
+      navigator.serviceWorker.getRegistrations().then(function(regs) {
+        regs.forEach(function(r) { r.unregister(); });
+      });
+      caches.keys().then(function(keys) {
+        keys.forEach(function(k) { caches.delete(k); });
+      });
+    }
+  </script>
   <script>
     (function () {
       var palettes = {