feat(settings): About section — vendor, versions, license, contact

Procurement personas found no vendor, version, license, or
support information anywhere in the app (a hard checklist fail
for regulated buyers). Settings gains an About category:
product name, Studio + running-hub version, vendor Flemming.AI,
author, Apache 2.0 license, contact address, and the docs URL —
every value selectable and one-click copyable. Studio version
constant moved to data/about_info.dart so sidebar tag and About
can never drift. Bumps Studio to 0.71.0.

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

lib/widgets/chain_settings_dialog.dart

@@ -4,7 +4,9 @@
 
 import 'package:chain_client_sdk/chain_client_sdk.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart' show Clipboard, ClipboardData;
 
+import '../data/about_info.dart';
 import '../data/error_presentation.dart';
 import '../data/hub.dart';
 import '../data/hub_auth_token.dart';
@@ -41,7 +43,15 @@ class ChainSettingsDialog extends StatefulWidget {
 /// Sidebar categories — every Settings panel belongs to exactly
 /// one. Order here drives the sidebar order and the
 /// first-opened category.
-enum _Category { general, appearance, ai, integrations, security, maintenance }
+enum _Category {
+  general,
+  appearance,
+  ai,
+  integrations,
+  security,
+  maintenance,
+  about,
+}
 
 class _FaiSettingsDialogState extends State<ChainSettingsDialog> {
   late final TextEditingController _host;
@@ -70,6 +80,10 @@ class _FaiSettingsDialogState extends State<ChainSettingsDialog> {
   /// auth-policy panel below re-queries with the new credentials.
   int _authPolicyReloadTick = 0;
 
+  /// Running hub's version for the About panel. Null while
+  /// loading, empty string when the hub is unreachable.
+  String? _hubVersion;
+
   @override
   void initState() {
     super.initState();
@@ -83,6 +97,13 @@ class _FaiSettingsDialogState extends State<ChainSettingsDialog> {
     _loadN8nEndpoints();
     _loadRegistryToken();
     _loadHubAuthToken();
+    _loadHubVersion();
+  }
+
+  Future<void> _loadHubVersion() async {
+    final v = await HubService.instance.hubVersion();
+    if (!mounted) return;
+    setState(() => _hubVersion = v);
   }
 
   Future<void> _loadHubAuthToken() async {
@@ -392,6 +413,7 @@ class _FaiSettingsDialogState extends State<ChainSettingsDialog> {
       _Category.integrations => _integrationsPanel(l, theme),
       _Category.security => _securityPanel(l, theme),
       _Category.maintenance => _maintenancePanel(l, theme),
+      _Category.about => _aboutPanel(l, theme),
     };
     return SingleChildScrollView(
       padding: const EdgeInsets.fromLTRB(
@@ -621,6 +643,39 @@ class _FaiSettingsDialogState extends State<ChainSettingsDialog> {
     ];
   }
 
+  List<Widget> _aboutPanel(AppLocalizations l, ThemeData theme) {
+    // Procurement-facing identity: who makes this, which
+    // versions run, under which license, whom to contact.
+    // Every value is selectable AND has a copy affordance.
+    return [
+      _panelTitle(l.aboutPanelTitle, l.aboutPanelBody, theme),
+      _AboutRow(label: l.aboutProduct, value: kProductName),
+      _AboutRow(label: l.aboutStudioVersion, value: kStudioVersion),
+      _AboutRow(
+        label: l.aboutHubVersion,
+        value: _hubVersion == null
+            ? '…'
+            : _hubVersion!.isEmpty
+                ? l.aboutHubVersionUnknown
+                : _hubVersion!,
+      ),
+      _AboutRow(label: l.aboutVendor, value: kVendorName),
+      _AboutRow(label: l.aboutAuthor, value: kAuthorName),
+      _AboutRow(label: l.aboutLicense, value: kLicenseName),
+      _AboutRow(label: l.aboutContact, value: kContactEmail),
+      _AboutRow(
+        label: l.aboutDocs,
+        value: kDocsUrl,
+        trailing: IconButton(
+          icon: const Icon(Icons.open_in_new, size: 16),
+          tooltip: l.aboutOpenLink,
+          visualDensity: VisualDensity.compact,
+          onPressed: () => SystemActions.openInOs(kDocsUrl),
+        ),
+      ),
+    ];
+  }
+
   List<Widget> _aiPanel(AppLocalizations l, ThemeData theme) {
     return [
       _panelTitle(
@@ -779,6 +834,55 @@ class _FaiSettingsDialogState extends State<ChainSettingsDialog> {
   }
 }
 
+/// Label/value row of the About panel. The value is selectable
+/// and carries an explicit copy button (procurement reviewers
+/// paste these into checklists).
+class _AboutRow extends StatelessWidget {
+  final String label;
+  final String value;
+  final Widget? trailing;
+
+  const _AboutRow({required this.label, required this.value, this.trailing});
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final l = AppLocalizations.of(context)!;
+    return Padding(
+      padding: const EdgeInsets.symmetric(vertical: ChainSpace.xs),
+      child: Row(
+        children: [
+          SizedBox(
+            width: 150,
+            child: Text(
+              label,
+              style: theme.textTheme.bodySmall?.copyWith(
+                color: theme.colorScheme.onSurfaceVariant,
+              ),
+            ),
+          ),
+          Expanded(
+            child: SelectableText(value, style: theme.textTheme.bodyMedium),
+          ),
+          IconButton(
+            icon: const Icon(Icons.copy_outlined, size: 14),
+            tooltip: l.aboutCopyTooltip,
+            visualDensity: VisualDensity.compact,
+            onPressed: () async {
+              await Clipboard.setData(ClipboardData(text: value));
+              if (!context.mounted) return;
+              ScaffoldMessenger.of(context).showSnackBar(
+                SnackBar(content: Text(l.aboutCopiedToast)),
+              );
+            },
+          ),
+          ?trailing,
+        ],
+      ),
+    );
+  }
+}
+
 class _ChannelRow extends StatelessWidget {
   final ChannelInfo channel;
   final bool active;
@@ -2635,6 +2739,7 @@ class _Sidebar extends StatelessWidget {
         Icons.build_outlined,
         l.settingsCategoryMaintenance,
       ),
+      (_Category.about, Icons.info_outline, l.settingsCategoryAbout),
     ];
     return SizedBox(
       width: 220,