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/__init__.py

@@ -0,0 +1,38 @@
+"""Pydantic schemas — re-exported for convenient imports."""
+
+from app.schemas.auth import LoginRequest, TokenResponse, UserOut
+
+from app.schemas.technique import (
+    TechniqueCreate,
+    TechniqueOut,
+    TechniqueSummary,
+    TechniqueUpdate,
+)
+
+from app.schemas.test import (
+    TestCreate,
+    TestOut,
+    TestUpdate,
+    TestValidate,
+)
+
+from app.schemas.evidence import EvidenceOut
+
+__all__ = [
+    # Auth
+    "LoginRequest",
+    "TokenResponse",
+    "UserOut",
+    # Technique
+    "TechniqueCreate",
+    "TechniqueOut",
+    "TechniqueSummary",
+    "TechniqueUpdate",
+    # Test
+    "TestCreate",
+    "TestOut",
+    "TestUpdate",
+    "TestValidate",
+    # Evidence
+    "EvidenceOut",
+]