feat(studio): localise Settings sidebar + add inline help docs + Approvals doc

Three operator-UX gaps closed:

  - Settings dialog's six-category sidebar (General / Appearance /
    System AI / Integrations / Security / Maintenance) was
    hardcoded English; now flows through AppLocalizations
    ("Allgemein" / "Darstellung" / "System-KI" / "Integrationen" /
    "Sicherheit" / "Wartung"). Same for the per-panel title +
    description.
  - Per-channel daemon-action labels ('enable autostart' /
    'disable autostart' / 'daemon restart' etc.) and the
    OK / Failed result line in the toast also moved to l10n,
    so the system-action feedback reads as one language.
  - New 'Approvals' doc bundle (en + de) under assets/docs/,
    registered as a fifth doc card on Welcome plus exposed via
    the new public  helper. The
    Approvals, Audit and Doctor app-bars grow a Help icon button
    next to Refresh that opens the matching doc in the existing
    bottom-sheet reader — no extra screen, no learning curve.

Studio bumped to 0.67.0; editor path-override pulls in 0.20.1
(flow-list row polish).

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/pages/welcome.dart

@@ -829,8 +829,27 @@ final List<_DocEntry> _kDocs = <_DocEntry>[
     title: (l) => l.welcomeDocFlowsTitle,
     blurb: (l) => l.welcomeDocFlowsBlurb,
   ),
+  _DocEntry(
+    slug: 'approvals',
+    icon: Icons.gavel_outlined,
+    title: (l) => l.welcomeDocApprovalsTitle,
+    blurb: (l) => l.welcomeDocApprovalsBlurb,
+  ),
 ];
 
+/// Public entry-point for the doc-reader sheet. Pass a slug
+/// ("approvals", "audit", "security", "architecture", "flows")
+/// and the bottom sheet opens with the localized markdown.
+/// Returns null when the slug isn't registered — caller can
+/// log + show a SnackBar.
+Future<void>? showFaiDoc(BuildContext context, String slug) {
+  final entry = _kDocs.firstWhere(
+    (d) => d.slug == slug,
+    orElse: () => _kDocs.first,
+  );
+  return _DocReaderSheet.show(context, entry);
+}
+
 /// Two-by-two doc grid on wide windows, single column on
 /// narrow. Each card opens `_DocReaderSheet` for its slug.
 class _DocsRow extends StatelessWidget {