refactor(settings/audit): conditional retention disclosure + flat layout

Drops the wrapping details-card so the audit toggle and retention input
read like the email page. The audit switch now uses role="switch" and a
new app-settings-audit component (built on the existing
createConditionalToggleInit primitive) hides the retention block when
audit is disabled — the input is meaningless without audit on, and the
control state syncs automatically on toggle. The redundant info
blockquote and the toggle's paraphrased DB description are gone.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/js/app-init.js

@@ -20,6 +20,7 @@ import { initCustomFieldOptionsToggle } from './components/app-custom-field-opti
 import { initTenantSsoToggle } from './components/app-tenant-sso-toggle.js';
 import { initTenantLdapToggle } from './components/app-tenant-ldap-toggle.js';
 import { initTelemetrySettings } from './components/app-settings-telemetry.js';
+import { initSettingsAudit } from './components/app-settings-audit.js';
 import { initStandardDetailPages } from './components/app-standard-detail-page.js';
 import { initAutoSubmit } from './components/app-auto-submit.js';
 import { initTabs } from './components/app-tabs.js';
@@ -196,6 +197,10 @@ const bootRuntime = async () => {
     scope: 'global',
     configPath: 'components.settingsTelemetry',
   });
+  runtime.register('settings-audit', initSettingsAudit, {
+    scope: 'global',
+    configPath: 'components.settingsAudit',
+  });
   runtime.register('auto-submit', initAutoSubmit, {
     scope: 'global',
     configPath: 'components.autoSubmit',