fix(events): ArmStateFSM uses PBKDF2 via alerts.pin (issue #2)

Was: unsalted SHA-256 read from [system] arm_pin_hash.
Now: PBKDF2-SHA256 600k iterations read from [security] pin_hash,
matching the web arm/disarm path and the alerts/pin module.

Also drops the redundant pin re-hash on the arm_state_log audit row
(a fresh PBKDF2 salt made the column valueless for traceability).

Part of issue #2 PIN hashing unification.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit/test_events.py

@@ -1,6 +1,5 @@
 """Tests for the Phase 6 events subsystem: rules, arm state FSM, history."""
 
-import hashlib
 import time
 
 import pytest
@@ -19,7 +18,7 @@ from vigilar.storage.queries import insert_event
 
 def _make_config(rules=None, pin_hash=""):
     return VigilarConfig(
-        system={"arm_pin_hash": pin_hash},
+        security={"pin_hash": pin_hash},
         cameras=[],
         sensors=[],
         rules=rules or [],
@@ -27,7 +26,8 @@ def _make_config(rules=None, pin_hash=""):
 
 
 def _pin_hash(pin: str) -> str:
-    return hashlib.sha256(pin.encode()).hexdigest()
+    from vigilar.alerts.pin import hash_pin
+    return hash_pin(pin)
 
 
 # ---------------------------------------------------------------------------

vigilar/events/state.py

@@ -1,12 +1,11 @@
 """Arm state finite state machine."""
 
-import hashlib
-import hmac
 import logging
 import time
 
 from sqlalchemy.engine import Engine
 
+from vigilar.alerts.pin import verify_pin as _verify_pin_hash
 from vigilar.config import VigilarConfig
 from vigilar.constants import ArmState, EventType, Severity, Topics
 from vigilar.storage.queries import get_current_arm_state, insert_arm_state, insert_event
@@ -19,7 +18,7 @@ class ArmStateFSM:
 
     def __init__(self, engine: Engine, config: VigilarConfig):
         self._engine = engine
-        self._pin_hash = config.system.arm_pin_hash
+        self._pin_hash = config.security.pin_hash
         self._state = ArmState.DISARMED
         self._bus = None
         self._load_initial_state()
@@ -43,12 +42,11 @@ class ArmStateFSM:
         return self._state
 
     def verify_pin(self, pin: str) -> bool:
-        """Verify a PIN against the stored hash using HMAC comparison."""
+        """Verify a PIN against the stored PBKDF2 hash."""
         if not self._pin_hash:
             # No PIN configured — allow all transitions
             return True
-        candidate = hashlib.sha256(pin.encode()).hexdigest()
-        return hmac.compare_digest(candidate, self._pin_hash)
+        return _verify_pin_hash(pin, self._pin_hash)
 
     def transition(
         self,
@@ -68,9 +66,8 @@ class ArmStateFSM:
         old_state = self._state
         self._state = new_state
 
-        # Log to database
-        pin_hash = hashlib.sha256(pin.encode()).hexdigest() if pin else None
-        insert_arm_state(self._engine, new_state.value, triggered_by, pin_hash)
+        # Log to database (pin_hash column is no longer populated — see #2)
+        insert_arm_state(self._engine, new_state.value, triggered_by, None)
 
         # Log event
         insert_event(