fix: improve maintenance and synchronize live conversations

backend/tests/services/test_ticket_phase4.py

@@ -24,8 +24,8 @@ from uuid import uuid4
 import pytest
 
 from app.api.ticket_webhooks import _parse_alert
-from app.models.investigation import ProposalStatus, TicketProposal
-from app.models.ticket import Ticket, TicketPriority, TicketSource, TicketStatus
+from app.models.investigation import ProposalStatus
+from app.models.ticket import TicketSource, TicketStatus
 from app.models.ticket_activity import TicketActivity, TicketActivityType
 from app.services.ticket import TicketService
 from app.services.ticket_jira import should_escalate
@@ -214,7 +214,6 @@ class TestRunChaining:
         enqueueing the next one in the same session must work — the guard
         has to flush before checking for active runs."""
         from app.models.investigation import (
-            InvestigationRun,
             InvestigationRunStatus,
             InvestigationRunType,
         )