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/schemas/test_template.py

@@ -0,0 +1,75 @@
+"""Pydantic schemas for TestTemplate endpoints."""
+
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict
+
+
+# ── Full output ─────────────────────────────────────────────────────
+
+
+class TestTemplateOut(BaseModel):
+    """Complete representation of a test template."""
+
+    id: uuid.UUID
+    mitre_technique_id: str
+    name: str
+    description: str | None = None
+    source: str
+    source_url: str | None = None
+    attack_procedure: str | None = None
+    expected_detection: str | None = None
+    platform: str | None = None
+    tool_suggested: str | None = None
+    severity: str | None = None
+    atomic_test_id: str | None = None
+    is_active: bool = True
+    created_at: datetime | None = None
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+# ── Create ──────────────────────────────────────────────────────────
+
+
+class TestTemplateCreate(BaseModel):
+    """Payload for creating a custom test template."""
+
+    mitre_technique_id: str
+    name: str
+    description: str | None = None
+    source: str = "custom"
+    source_url: str | None = None
+    attack_procedure: str | None = None
+    expected_detection: str | None = None
+    platform: str | None = None
+    tool_suggested: str | None = None
+    severity: str | None = None
+    atomic_test_id: str | None = None
+
+
+# ── Summary (for listings) ─────────────────────────────────────────
+
+
+class TestTemplateSummary(BaseModel):
+    """Lightweight representation for listing templates."""
+
+    id: uuid.UUID
+    mitre_technique_id: str
+    name: str
+    source: str
+    platform: str | None = None
+    severity: str | None = None
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+# ── Instantiate (create a real Test from a template) ────────────────
+
+
+class TestTemplateInstantiate(BaseModel):
+    """Payload to create a real test from an existing template."""
+
+    template_id: uuid.UUID
+    technique_id: uuid.UUID