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/modal.js

@@ -6,9 +6,9 @@
  * avoid fighting with the main render cycle.
  */
 
-import { esc, att_esc } from '../helpers.js?v=9';
-import { apiSubmit } from '../api.js?v=9';
-import { createDom } from '../vdom.js?v=9';
+import { esc, att_esc } from '../helpers.js';
+import { apiSubmit } from '../api.js';
+import { createDom } from '../vdom.js';
 
 /**
  * Render Hoover VNodes into a modal content element.