feat(auth): add opaque bearer sessions

server/src/app/db/base.py

@@ -1,5 +1,4 @@
 from app.db.base_class import Base
-from app.models.agent_conversation import AgentConversation, AgentConversationMessage
 from app.models.agent_asset import (
     AgentAsset,
     AgentAssetReview,
@@ -7,14 +6,16 @@ from app.models.agent_asset import (
     AgentAssetTestRun,
     AgentAssetVersion,
 )
+from app.models.agent_conversation import AgentConversation, AgentConversationMessage
 from app.models.agent_feedback import AgentOperationFeedback
 from app.models.agent_run import AgentRun, AgentToolCall, AgentTraceEvent, SemanticParseLog
 from app.models.approval import ApprovalRecord
 from app.models.audit_log import AuditLog
+from app.models.auth_session import AuthSession
 from app.models.budget import BudgetAllocation, BudgetReservation, BudgetTransaction
-from app.models.employee_change_log import EmployeeChangeLog
-from app.models.employee_behavior_profile import EmployeeBehaviorProfileSnapshot
 from app.models.employee import Employee
+from app.models.employee_behavior_profile import EmployeeBehaviorProfileSnapshot
+from app.models.employee_change_log import EmployeeChangeLog
 from app.models.expense_case import BusinessEvent, ExpenseCase, ExpenseCaseLink
 from app.models.few_shot_sample import FewShotSample
 from app.models.financial_record import (
@@ -53,6 +54,7 @@ __all__ = [
     "AgentTraceEvent",
     "ApprovalRecord",
     "AuditLog",
+    "AuthSession",
     "BudgetAllocation",
     "BudgetReservation",
     "BudgetTransaction",