fix(keys): new passwords have at least 12 characters

The register can't check a password it never sees, and should its
database leak, the verifier and the keys wrapped under the password fall
to guessing at Argon2id's cost (the second reading's M8). Devices now
refuse a new password shorter than 12 characters, counted as code points
once normalised (halkyon_keys' checkNewPassword), at sign-up, a reset
keeping the keys and a change alike, before anything is derived; the new
password's field says so, and the refusal has its own text (en, de).
Signing in takes any length, so a password set before keeps working.

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

@@ -773,4 +773,14 @@ class HalkyonAppLocalizationsDe extends HalkyonAppLocalizations {
   @override
   String get passwordFailed =>
       'Die Instanz war nicht erreichbar. Prüf die Verbindung und versuch es noch einmal.';
+
+  @override
+  String passwordMinLength(int count) {
+    return 'Mindestens $count Zeichen';
+  }
+
+  @override
+  String passwordTooShort(int count) {
+    return 'Ein neues Passwort braucht mindestens $count Zeichen: Sollte die Datenbank der Instanz je nach außen gelangen, wird ein kurzes zuerst erraten.';
+  }
 }