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/hoover/index.js

@@ -35,7 +35,7 @@ export { scheduleTokenRefresh, cancelTokenRefresh, checkSession, logout, initAut
 export { modelRegister, getModel, modelFetch, collectLoadingModels } from './model.js';
 
 /* ── Helpers ─────────────────────────────────────────────────── */
-export { esc, att_esc, enc, $val, parseZones, downloadBlob } from './helpers.js';
+export { esc, att_esc, enc, $val, parseZones, fmtBytes, csvToArr, downloadBlob } from './helpers.js';
 
 /* ── UI Components: Layout ───────────────────────────────────── */
 export { PageHeader, renderGuard, renderGuardMulti, Tabs, SectionTitle, ActionGroup, DataTableSection } from './components/layout.js';