feat(store): trust gate before every module install

One-click installs showed no trust signal at all (top security
finding of the usertest panel). Every install path — store card,
detail sheet, and the flow list's quick fix — now routes through
one confirmation dialog showing what the hub actually knows
before download: origin store, version, license, maturity, and
required services/capabilities, plus the sandbox model and an
honest note that per-entry signature status is not in the store
index yet (verification happens hub-side at install). Widget
tests cover content and confirm/cancel semantics.

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

test/install_confirm_test.dart

@@ -0,0 +1,84 @@
+// Install trust gate — every install path routes through this
+// dialog, so it must show provenance (source, version, license,
+// maturity) and the honest signature note, and only proceed on
+// an explicit confirmation.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:chain_studio/data/hub.dart';
+import 'package:chain_studio/l10n/app_localizations.dart';
+import 'package:chain_studio/widgets/chain_install_confirm.dart';
+
+const _item = StoreItem(
+  name: 'text.extract',
+  taglineEn: '',
+  taglineDe: '',
+  descriptionEn: '',
+  descriptionDe: '',
+  category: 'text',
+  tags: [],
+  requiresCapabilities: [],
+  requiresServices: ['judge-ner'],
+  license: 'Apache-2.0',
+  repository: '',
+  bestVersion: '0.1.0',
+  status: 'alpha',
+  installed: false,
+  featured: false,
+  iconUrl: '',
+  screenshotUrls: [],
+  docsUrl: '',
+  kind: 'native',
+  provider: 'fai',
+  source: 'bundled',
+);
+
+Widget _host({required void Function(bool) onResult}) => MaterialApp(
+      localizationsDelegates: AppLocalizations.localizationsDelegates,
+      supportedLocales: AppLocalizations.supportedLocales,
+      locale: const Locale('de'),
+      home: Builder(
+        builder: (context) => Center(
+          child: ElevatedButton(
+            onPressed: () async {
+              onResult(await ChainInstallConfirmDialog.show(context, _item));
+            },
+            child: const Text('go'),
+          ),
+        ),
+      ),
+    );
+
+void main() {
+  testWidgets('shows provenance, maturity, and the signature note',
+      (tester) async {
+    await tester.pumpWidget(_host(onResult: (_) {}));
+    await tester.tap(find.text('go'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('„text.extract" installieren?'), findsOneWidget);
+    expect(find.text('v0.1.0'), findsOneWidget);
+    expect(find.text('Mitgelieferter Store-Index'), findsOneWidget);
+    expect(find.text('Apache-2.0'), findsOneWidget);
+    expect(find.text('experimentell'), findsOneWidget);
+    expect(find.text('judge-ner'), findsOneWidget);
+    expect(find.textContaining('Signaturen prüft der Hub'), findsOneWidget);
+  });
+
+  testWidgets('cancel returns false, install returns true', (tester) async {
+    bool? result;
+    await tester.pumpWidget(_host(onResult: (r) => result = r));
+    await tester.tap(find.text('go'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('Abbrechen'));
+    await tester.pumpAndSettle();
+    expect(result, isFalse);
+
+    await tester.tap(find.text('go'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('Installieren'));
+    await tester.pumpAndSettle();
+    expect(result, isTrue);
+  });
+}