refactor: extract shared utilities and standardize page patterns

- Add fmtBytes() and csvToArr() helpers to hoover/helpers.js
- Replace inline async patterns with ActionButton/ConfirmDelete in wireguard.js
- Convert addDomain/editDomain to QuickModal + apiSubmit in proxy.js
- Convert settingsModal handlers to formAction in certs.js
- Remove redundant synced handling from dhcp.js apply button
- Add onComplete callback to ConfirmDelete (fixes users.js onRefresh bug)
- Fix passkeys.js ActionCell/Table usage (invalid component API)
- Remove duplicate fmtBytes from dashboard.js

webui/static/pages/dashboard.js

@@ -1,12 +1,4 @@
-import { html, PageHeader, definePage, getModel, renderGuardMulti, ServiceStatus, StatCard, Table, Badge, ActionButton } from '/static/hoover/index.js';
-
-function fmtBytes(bytes) {
-    if (bytes === 0) return '0 B';
-    const k = 1024;
-    const sizes = ['B', 'KB', 'MB', 'GB', 'TB'];
-    const i = Math.floor(Math.log(bytes) / Math.log(k));
-    return (bytes / Math.pow(k, i)).toFixed(i > 0 ? 1 : 0) + ' ' + sizes[i];
-}
+import { html, PageHeader, definePage, getModel, renderGuardMulti, ServiceStatus, StatCard, Table, Badge, ActionButton, fmtBytes } from '/static/hoover/index.js';
 
 export default definePage({
     init() {