refactor(arch): eliminate all cross-module model imports in service layer

Enforce MOD-025/MOD-026 rules: zero top-level cross-module model imports
remain in any service file. All 66 files migrated using deferred import
patterns (method-body, _get_model() helpers, instance-cached self._Model)
and new cross-module service methods in tenancy. Documentation updated
with Pattern 6 (deferred imports), migration plan marked complete, and
violations status reflects 84→0 service-layer violations.

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

app/modules/monitoring/services/audit_provider.py

@@ -8,16 +8,11 @@ AuditProviderProtocol interface.
 """
 
 import logging
-from typing import TYPE_CHECKING
 
 from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.orm import Session
 
 from app.modules.contracts.audit import AuditEvent
-from app.modules.tenancy.models import AdminAuditLog
-
-if TYPE_CHECKING:
-    pass
 
 logger = logging.getLogger(__name__)
 
@@ -46,6 +41,8 @@ class DatabaseAuditProvider:
             True if logged successfully, False otherwise
         """
         try:
+            from app.modules.tenancy.models import AdminAuditLog
+
             audit_log = AdminAuditLog(
                 admin_user_id=event.admin_user_id,
                 action=event.action,