refactor(pep8): enforce full PEP8 compliance across backend Python codebase

- ruff.toml: select E/W/F/I/N rules, line-length=120, drop legacy ignores
- Auto-fix: sort 82 import blocks (isort), remove 29 unused imports,
  strip 6 trailing-whitespace blank lines in docstrings
- main.py: move setup_logging and settings imports to top (E402)
- errors.py: noqa N818 on DDD exception names (96 call sites, safe)
- intel_service.py: noqa N817 for universal ET alias
- atomic/elastic/sigma import services: move _MAX_UNCOMPRESSED_SIZE and
  _MAX_ENTRIES to module level (N806)
- compliance_import_service.py: move SAMPLE_CONTROLS / CIS_CONTROLS to
  module level; wrap long description strings (N806 + E501)
- snapshot_service.py: move STATUS_ORDER dict to module level (N806)
- sigma_import_service.py: remove dead dedup_key expression (F841)
- threat_actor_import_service.py: remove dead stix_to_actor expression (F841)
- data_source.py, seed_demo.py, campaign_scheduler_service.py,
  lolbas_import_service.py: wrap lines exceeding 120 chars (E501)
- d3fend_import_service.py: per-file E501 ignore (data file with long strings)

All 439 unit tests pass. ruff check app/ → All checks passed!

backend/app/routers/tests.py

@@ -26,49 +26,84 @@ from sqlalchemy.orm import Session
 
 from app.database import get_db
 from app.dependencies.auth import get_current_user, require_any_role, require_role
-from app.domain.enums import DataClassification
+from app.domain.unit_of_work import UnitOfWork
 from app.limiter import limiter
 from app.models.enums import TestState
 from app.models.user import User
 from app.schemas.test import (
+    TestBlueUpdate,
+    TestBlueValidate,
+    TestClassificationUpdate,
     TestCreate,
     TestOut,
-    TestUpdate,
     TestRedUpdate,
-    TestBlueUpdate,
     TestRedValidate,
-    TestBlueValidate,
     TestRemediationUpdate,
-    TestClassificationUpdate,
+    TestUpdate,
 )
 from app.schemas.test_template import TestTemplateInstantiate
-from app.domain.unit_of_work import UnitOfWork
 from app.services.audit_service import log_action
 from app.services.status_service import recalculate_technique_status
 from app.services.test_crud_service import (
     create_test as crud_create_test,
+)
+from app.services.test_crud_service import (
     create_test_from_template as crud_create_from_template,
+)
+from app.services.test_crud_service import (
     get_test_detail as crud_get_test_detail,
+)
+from app.services.test_crud_service import (
     get_test_or_raise as crud_get_test_or_raise,
+)
+from app.services.test_crud_service import (
     get_test_timeline as crud_get_test_timeline,
+)
+from app.services.test_crud_service import (
     get_test_with_technique as crud_get_test_with_technique,
+)
+from app.services.test_crud_service import (
     list_tests as crud_list_tests,
+)
+from app.services.test_crud_service import (
     update_test as crud_update_test,
+)
+from app.services.test_crud_service import (
     update_test_blue as crud_update_test_blue,
+)
+from app.services.test_crud_service import (
     update_test_red as crud_update_test_red,
 )
 from app.services.test_workflow_service import (
-    start_execution as wf_start_execution,
-    submit_red_evidence as wf_submit_red,
-    submit_blue_evidence as wf_submit_blue,
-    validate_as_red_lead as wf_validate_red,
-    validate_as_blue_lead as wf_validate_blue,
-    reopen_test as wf_reopen,
-    handle_remediation_completed as wf_handle_remediation,
     get_retest_chain as wf_get_retest_chain,
+)
+from app.services.test_workflow_service import (
+    handle_remediation_completed as wf_handle_remediation,
+)
+from app.services.test_workflow_service import (
     pause_timer as wf_pause_timer,
+)
+from app.services.test_workflow_service import (
+    reopen_test as wf_reopen,
+)
+from app.services.test_workflow_service import (
     resume_timer as wf_resume_timer,
 )
+from app.services.test_workflow_service import (
+    start_execution as wf_start_execution,
+)
+from app.services.test_workflow_service import (
+    submit_blue_evidence as wf_submit_blue,
+)
+from app.services.test_workflow_service import (
+    submit_red_evidence as wf_submit_red,
+)
+from app.services.test_workflow_service import (
+    validate_as_blue_lead as wf_validate_blue,
+)
+from app.services.test_workflow_service import (
+    validate_as_red_lead as wf_validate_red,
+)
 
 router = APIRouter(prefix="/tests", tags=["tests"])