fix(l10n): consistent formal address across the German catalog

Store search, security panel, System-AI fix hint and the
approvals payload hint addressed the operator informally while
the rest of the app uses Sie — the panel flagged the break on
every second screen. All DE strings now use the formal address,
and a guard test rejects any future informal form in app_de.arb.

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

test/l10n_formality_test.dart

@@ -0,0 +1,43 @@
+// German strings address the operator as "Sie" — never "Du".
+// The usertest panel flagged Du/Sie breaks (store search, flow
+// empty states) as a recurring trust issue for the regulated
+// audience, so this guard scans the DE catalog for unambiguous
+// second-person-singular forms. Progress messages in the first
+// person ("Starte …" = the app announcing its own action) stay
+// legal; only forms that address the reader are rejected.
+
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('DE catalog contains no informal (Du) address', () {
+    final raw = File('lib/l10n/app_de.arb').readAsStringSync();
+    final map = jsonDecode(raw) as Map<String, dynamic>;
+    // Pronouns + possessives + common 2nd-person-singular verb
+    // forms. Word-bounded so "individuell" or "Bedingungen"
+    // never match.
+    final informal = RegExp(
+      r"\b(du|dich|dir|dein|deine|deiner|deinem|deinen|deins|"
+      r"brauchst|tippst|willst|kannst|hast|bist|machst|siehst|"
+      r"klickst|wählst|öffnest|startest|versuchst|versuch's)\b",
+      caseSensitive: false,
+    );
+    final offenders = <String>[];
+    map.forEach((key, value) {
+      if (key.startsWith('@') || value is! String) return;
+      final m = informal.firstMatch(value);
+      if (m != null) {
+        offenders.add('$key: "${m.group(0)}" in "$value"');
+      }
+    });
+    expect(
+      offenders,
+      isEmpty,
+      reason:
+          'German UI strings must use the formal Sie address:\n'
+          '${offenders.join('\n')}',
+    );
+  });
+}