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/zones.js

@@ -1,4 +1,4 @@
-import { html, PageHeader, Badge, Empty, ConfirmDelete, renderGuard, enc, esc, $val, definePage, getModel, MultiSelectModal, QuickModal } from '/static/hoover/index.js?v=10';
+import { html, PageHeader, Badge, Empty, ConfirmDelete, renderGuard, enc, esc, $val, definePage, getModel, MultiSelectModal, QuickModal } from '/static/hoover/index.js';
 
 const addZone = QuickModal({
     title: 'Add Zone',