feat(F4): add PIN hashing utilities with PBKDF2-SHA256

tests/unit/test_pin.py

@@ -0,0 +1,39 @@
+"""Tests for PIN hashing and verification."""
+
+from vigilar.alerts.pin import hash_pin, verify_pin
+
+
+def test_hash_pin_returns_formatted_string():
+    result = hash_pin("1234")
+    parts = result.split("$")
+    assert len(parts) == 3
+    assert parts[0] == "pbkdf2_sha256"
+    assert len(parts[1]) == 32  # 16 bytes hex = 32 chars
+    assert len(parts[2]) == 64  # 32 bytes hex = 64 chars
+
+
+def test_verify_pin_correct():
+    stored = hash_pin("5678")
+    assert verify_pin("5678", stored) is True
+
+
+def test_verify_pin_wrong():
+    stored = hash_pin("5678")
+    assert verify_pin("0000", stored) is False
+
+
+def test_verify_pin_empty_hash_returns_true():
+    assert verify_pin("1234", "") is True
+    assert verify_pin("", "") is True
+
+
+def test_hash_pin_different_salts():
+    h1 = hash_pin("1234")
+    h2 = hash_pin("1234")
+    assert h1 != h2
+
+
+def test_verify_pin_handles_unicode():
+    stored = hash_pin("p@ss!")
+    assert verify_pin("p@ss!", stored) is True
+    assert verify_pin("p@ss?", stored) is False