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/users.js

@@ -222,7 +222,7 @@ function UsersPage() {
                         deleteKey=${u.username}
                         message=${'Delete user ' + esc(u.username) + '? This cannot be undone.'}
                         success=${'User ' + esc(u.username) + ' deleted'}
-                        onRefresh=${() => loadUsers()} />`}
+                        onComplete=${() => loadUsers()} />`}
             </td>
         </tr>`;
     });