feat: Phase 3 - CRUD core for Techniques, Tests and Evidence (T-014 to T-017)

- Add Pydantic schemas for Technique, Test and Evidence
- Add CRUD endpoints for Techniques (list with filters, detail, create, update, review)
- Add CRUD endpoints for Tests (create, detail, update, validate, reject)
- Add evidence upload with SHA-256 integrity and presigned download URLs
- Add MinIO/S3 storage client with bucket auto-creation on startup
- Add status_service to recalculate technique coverage from test results
- Add require_any_role RBAC dependency for multi-role authorization
- Update README with API endpoints reference and project structure

backend/app/schemas/evidence.py

@@ -0,0 +1,23 @@
+"""Pydantic schemas for Evidence endpoints."""
+
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict
+
+
+class EvidenceOut(BaseModel):
+    """Representation of an evidence record returned by the API.
+
+    ``download_url`` is a presigned URL generated at response time.
+    """
+
+    id: uuid.UUID
+    test_id: uuid.UUID
+    file_name: str
+    sha256_hash: str
+    uploaded_by: uuid.UUID | None = None
+    uploaded_at: datetime | None = None
+    download_url: str | None = None
+
+    model_config = ConfigDict(from_attributes=True)