fix zombie leak, add quiet-hours toggle, improve query reply, configurable router threshold, JS dashboard

cmd/mavweb/static/service-worker.js

@@ -0,0 +1,16 @@
+const CACHE = "maven-v2";
+self.addEventListener("install", e => {
+  e.waitUntil(caches.open(CACHE).then(c => c.addAll(["/", "/manifest.json", "/dash"])));
+  self.skipWaiting();
+});
+self.addEventListener("activate", e => {
+  e.waitUntil(
+    caches.keys().then(keys => Promise.all(keys.filter(k => k !== CACHE).map(k => caches.delete(k))))
+  );
+  clients.claim();
+});
+self.addEventListener("fetch", e => {
+  e.respondWith(
+    fetch(e.request).catch(() => caches.match(e.request))
+  );
+});