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/test_template.py

@@ -0,0 +1,45 @@
+"""TestTemplate model — predefined test catalog entries."""
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import Column, String, Text, Boolean, DateTime, Index
+from sqlalchemy.dialects.postgresql import UUID
+
+from app.database import Base
+
+
+class TestTemplate(Base):
+    """
+    Predefined test template mapped to a MITRE ATT&CK technique.
+
+    Templates come from several sources:
+      - **atomic_red_team**: Atomic Red Team by Red Canary
+      - **mitre**: MITRE ATT&CK procedure examples
+      - **custom**: Manually created by teams
+
+    Users can instantiate a real Test from a template.
+    """
+    __tablename__ = "test_templates"
+
+    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    mitre_technique_id = Column(String, nullable=False)          # e.g. "T1059.001"
+    name = Column(String, nullable=False)
+    description = Column(Text, nullable=True)
+    source = Column(String, nullable=False)                      # atomic_red_team / mitre / custom
+    source_url = Column(String, nullable=True)
+    attack_procedure = Column(Text, nullable=True)               # Suggested attack procedure
+    expected_detection = Column(Text, nullable=True)             # What blue team should detect
+    platform = Column(String, nullable=True)                     # windows / linux / macos
+    tool_suggested = Column(String, nullable=True)
+    severity = Column(String, nullable=True)                     # low / medium / high / critical
+    atomic_test_id = Column(String, nullable=True)               # ID in Atomic Red Team repo
+    is_active = Column(Boolean, default=True)
+    created_at = Column(DateTime, default=datetime.utcnow)
+
+    __table_args__ = (
+        Index('ix_test_templates_mitre_technique_id', 'mitre_technique_id'),
+        Index('ix_test_templates_source', 'source'),
+        Index('ix_test_templates_platform', 'platform'),
+        Index('ix_test_templates_severity', 'severity'),
+    )