fix(arch-014,arch-020): no contract lazy-resurrect after unregister; event bus dedupes handlers

Also fixes ARCH-029/041: none-check before attribute access in trigger dispatcher.

app/core/trigger_dispatcher.py

@@ -121,11 +121,14 @@ class TriggerDispatcher:
         """Query DB for active automations matching *event_name* and dispatch."""
         from app.core.db import get_session_factory
         from app.plugins.builtins.contracts import get_contract
+        # None-check FIRST — accessing attributes on the contract before the
+        # check crashed with AttributeError when automation was inactive
+        # (ARCH-029/041).
         automation_contract = get_contract("automation")
-        AutomationDefinition = automation_contract.Automation  # noqa: N806
         if automation_contract is None:
             logger.debug("Automation plugin not available — trigger skipped")
             return
+        AutomationDefinition = automation_contract.Automation  # noqa: N806
 
         factory = get_session_factory()
         tenant_id = payload.get("tenant_id")