feat(app): an authenticator's key copied, marked sensitive, and its code six digits

A phone without a camera whose authenticator doesn't open otpauth: had no
way but typing the key. It is copied again, the key alone (ADR 0017
amended, the developer's decision of 3 Nov 2026): on Android through each
app's SensitiveClipboard.kt, marked EXTRA_IS_SENSITIVE, so Gboard and the
system show no preview and keep it out of their histories; elsewhere through
Flutter's clipboard. Emptied 60 seconds later if the clipboard still holds
it. The recovery phrase and codes stay never copied.

The code's field counted "/7", taking an optional space for a seventh
character: it now takes six digits alone, a pasted space dropped, and counts
nothing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_app/lib/l10n/halkyon_app_localizations_de.dart

@@ -485,6 +485,10 @@ class HalkyonAppLocalizationsDe extends HalkyonAppLocalizations {
   @override
   String get passwordAuthenticatorKey => 'Schlüssel';
 
+  @override
+  String get passwordAuthenticatorKeyCopied =>
+      'Schlüssel kopiert. In einer Minute wird er aus der Zwischenablage entfernt.';
+
   @override
   String get passwordAuthenticatorOpen => 'In deiner Authenticator-App öffnen';