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!

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

backend/app/routers/scores.py

@@ -13,17 +13,16 @@ from app.database import get_db
 from app.dependencies.auth import get_current_user, require_role
 from app.domain.unit_of_work import UnitOfWork
 from app.models.user import User
-from app.services.scoring_service import (
-    score_technique_by_mitre_id,
-    score_actor_by_id,
-    calculate_tactic_score,
-    calculate_organization_score,
-    get_score_history,
-)
 from app.services.scoring_config_service import (
     get_weights_dict,
     update_scoring_weights,
 )
+from app.services.scoring_service import (
+    calculate_tactic_score,
+    get_score_history,
+    score_actor_by_id,
+    score_technique_by_mitre_id,
+)
 
 router = APIRouter(prefix="/scores", tags=["scores"])