feat(audit): free-text search, JSONL export of the view, labeled dev reset

- search field over flow/step/module/error/detail/project/id backs
  the list and the export ('current view' semantics); match logic
  is a top-level function with unit tests
- export writes one JSON object per line via the save dialog; the
  CLI stays the canonical WORM-grade export
- the bare trash icon on the audit toolbar read as 'delete
  evidence' (security-auditor finding) — the dev-only reset now
  sits in a labeled overflow menu next to the export action

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

test/audit_filter_test.dart

@@ -0,0 +1,49 @@
+// Free-text audit search — the match function behind the audit
+// page's search field and JSONL export ("current view" semantics).
+
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:chain_studio/data/hub.dart';
+import 'package:chain_studio/pages/audit.dart';
+
+AuditEvent _event({
+  String type = 'step.completed',
+  String? flow,
+  String? step,
+  String? module,
+  String? error,
+  String? detail,
+  String project = '',
+}) {
+  return AuditEvent(
+    eventId: 'evt-1',
+    timestamp: DateTime.utc(2026, 7, 18),
+    type: type,
+    flowName: flow,
+    stepId: step,
+    moduleName: module,
+    error: error,
+    detail: detail,
+    project: project,
+  );
+}
+
+void main() {
+  test('matches on every displayed field, case-insensitive', () {
+    expect(matchesAuditQuery(_event(flow: 'Rechnungslauf'), 'rechnung'), isTrue);
+    expect(matchesAuditQuery(_event(step: 'extract'), 'extract'), isTrue);
+    expect(matchesAuditQuery(_event(module: 'debug.echo'), 'echo'), isTrue);
+    expect(matchesAuditQuery(_event(error: 'Timeout nach 30s'), 'timeout'),
+        isTrue);
+    expect(matchesAuditQuery(_event(detail: '{"anchor":"tsa"}'), 'anchor'),
+        isTrue);
+    expect(matchesAuditQuery(_event(project: 'stromnetz'), 'strom'), isTrue);
+    expect(matchesAuditQuery(_event(), 'evt-1'), isTrue);
+    expect(matchesAuditQuery(_event(), 'step.'), isTrue);
+  });
+
+  test('rejects non-matching queries and null fields', () {
+    expect(matchesAuditQuery(_event(), 'nichtvorhanden'), isFalse);
+    expect(matchesAuditQuery(_event(flow: null, error: null), 'flow'), isFalse);
+  });
+}