feat: Faillock-Warnung bei wiederholten Fehlversuchen

Zeigt nach dem 2. fehlgeschlagenen Login-Versuch einen Hinweis an,
dass das Konto nach dem nächsten Fehlversuch gesperrt werden kann
(faillock default: 3 Versuche).

tests/test_integration.py

@@ -10,6 +10,7 @@ from pathlib import Path
 
 import pytest
 
+from moongreet.greeter import faillock_warning, FAILLOCK_MAX_ATTEMPTS
 from moongreet.ipc import create_session, post_auth_response, start_session, cancel_session
 
 
@@ -177,6 +178,31 @@ class TestLoginFlow:
         assert mock.received[1] == {"type": "cancel_session"}
 
 
+class TestFaillockWarning:
+    """Tests for the faillock warning message logic."""
+
+    def test_no_warning_on_first_attempt(self) -> None:
+        assert faillock_warning(1) is None
+
+    def test_warning_on_second_attempt(self) -> None:
+        warning = faillock_warning(2)
+        assert warning is not None
+        assert "1" in warning  # 1 Versuch übrig
+
+    def test_warning_on_third_attempt(self) -> None:
+        warning = faillock_warning(3)
+        assert warning is not None
+        assert "gesperrt" in warning.lower()
+
+    def test_warning_beyond_max_attempts(self) -> None:
+        warning = faillock_warning(4)
+        assert warning is not None
+        assert "gesperrt" in warning.lower()
+
+    def test_max_attempts_constant_is_three(self) -> None:
+        assert FAILLOCK_MAX_ATTEMPTS == 3
+
+
 class TestLastUser:
     """Tests for saving and loading the last logged-in user."""