Remove query-string cache-busting from static assets

Drop ?v=N version pins from all JS imports and HTML <link>/<script> tags.
Cache invalidation is now handled solely by server-side cache-control headers.
Update docs and AGENTS.md accordingly.

webui/static/pages/interfaces.js

@@ -1,4 +1,4 @@
-import { html, PageHeader, Table, renderGuardMulti, enc, $val, apiFetch, toast, definePage, getModel, modelFetch, StatusText, QuickModal, ZoneSelect } from '/static/hoover/index.js?v=10';
+import { html, PageHeader, Table, renderGuardMulti, enc, $val, apiFetch, toast, definePage, getModel, modelFetch, StatusText, QuickModal, ZoneSelect } from '/static/hoover/index.js';
 
 async function changeZone(name, zone, state) {
     const r = await apiFetch('/api/firewall/zones/' + enc(zone) + '/interfaces', {