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/hoover/components/qr.js

@@ -5,8 +5,8 @@
  * Uses qrcode-svg library for generation.
  */
 
-import { h } from '../vdom.js?v=9';
-import { esc } from '../helpers.js?v=9';
+import { h } from '../vdom.js';
+import { esc } from '../helpers.js';
 import QRCode from '../../../vendor/qrcode-svg-1.1.0.js';
 
 /**