feat(phase-11): implement Red/Blue business logic services (T-106, T-107, T-108)

T-106: Create test_workflow_service.py with state-machine transitions for the complete test lifecycle (draft -> red_executing -> blue_evaluating -> in_review -> validated/rejected), dual validation by Red/Blue leads, and reopen capability with field cleanup.

T-107: Update status_service.py to use detection_result from Blue Team instead of legacy result field, and differentiate between partial progress (some validated) vs all-in-progress states.

T-108: Create atomic_import_service.py that downloads the Atomic Red Team repo as a ZIP (avoiding API rate limits), parses all atomics YAML files, and creates idempotent TestTemplate records mapped to MITRE techniques.

Includes validation tests for all three tasks (19 checks total).

backend/app/models/enums.py

@@ -12,11 +12,18 @@ class TechniqueStatus(str, enum.Enum):
 
 class TestState(str, enum.Enum):
     draft = "draft"
+    red_executing = "red_executing"          # Red Team documenting attack
+    blue_evaluating = "blue_evaluating"      # Blue Team evaluating detection
     in_review = "in_review"
     validated = "validated"
     rejected = "rejected"
 
 
+class TeamSide(str, enum.Enum):
+    red = "red"
+    blue = "blue"
+
+
 class TestResult(str, enum.Enum):
     detected = "detected"
     not_detected = "not_detected"