feat: Implement artifact upload flow and storage (Task 006)

[Copilot]

• Explore repository structure and understand existing code
• Run existing tests (116 pass)
• Step 1: Create artifact type detector (src/backend/domains/artifacts/type_detector.py)
• Step 2: Add content hash helper (src/backend/domains/artifacts/content_hash.py)
• Step 3: Add publish_event method to EventGridPublisher + event type constants
• Step 4: Add blob upload/download methods to BlobService
• Step 5: Add blob_path field to Artifact model + update method to repository
• Step 6: Implement upload/download logic in ArtifactService
• Step 7: Add upload (POST 202) + download (GET) endpoints to artifact router
• Step 8: Add pyyaml dependency
• Step 9: Create backend tests (20 new tests — upload, type detection, download)
• Step 10: Create frontend components (artifact list, upload, status badge, hooks)
• Step 11: All 144 tests pass, linting clean, frontend builds
• Step 12: Code review — addressed ContentSettings fix
• Step 13: Security fix — replaced str(exc) with generic error message in upload endpoint
• Step 14: Merge main and fix CI test failures — updated 401 tests to work with auto-provisioning middleware

[christopherhouse]

@copilot Uh oh, thought you ran some tests to chck but looks lik a couple failed when running in CI.

=================================== FAILURES ===================================
______________ test_download_artifact_returns_401_without_tenant _______________

client = <httpx.AsyncClient object at 0x7f1ee0bcbc50>

    @pytest.mark.asyncio
    async def test_download_artifact_returns_401_without_tenant(client):
        """GET download without tenant context returns 401."""
        mock1, mock2, mock3 = _setup_context_mocks(None)
        with mock1, mock2, mock3:
            response = await client.get("/api/v1/projects/prj-001/artifacts/art-001/download")
>           assert response.status_code == 401
E           assert 500 == 401
E            +  where 500 = <Response [500 Internal Server Error]>.status_code

../../tests/backend/test_artifact_download.py:127: AssertionError
_______________ test_upload_artifact_returns_401_without_tenant ________________

client = <httpx.AsyncClient object at 0x7f1ee0af9260>

    @pytest.mark.asyncio
    async def test_upload_artifact_returns_401_without_tenant(client):
        """POST upload without tenant context returns 401."""
        mock1, mock2, mock3 = _setup_context_mocks(None)
        with mock1, mock2, mock3:
            response = await client.post(
                "/api/v1/projects/prj-001/artifacts",
                files={"file": ("test.json", b'{}', "application/json")},
            )
>           assert response.status_code == 401
E           assert 500 == 401
E            +  where 500 = <Response [500 Internal Server Error]>.status_code

../../tests/backend/test_artifact_upload.py:192: AssertionError
- generated xml file: /home/runner/work/Azure-Integration-Copilot/Azure-Integration-Copilot/test-results/backend-results.xml -
=========================== short test summary info ============================
FAILED test_artifact_download.py::test_download_artifact_returns_401_without_tenant - assert 500 == 401
 +  where 500 = <Response [500 Internal Server Error]>.status_code
FAILED test_artifact_upload.py::test_upload_artifact_returns_401_without_tenant - assert 500 == 401
 +  where 500 = <Response [500 Internal Server Error]>.status_code
======================== 2 failed, 142 passed in 1.06s =========================

[Copilot]

@copilot Uh oh, thought you ran some tests to chck but looks lik a couple failed when running in CI.

...

Fixed in da504b0. The CI failures were caused by the auto-provisioning tenant middleware merged from main. When _setup_context_mocks(None) mocked a valid user but None tenant, the updated middleware returned 500 ("Tenant not found") instead of passing through to the route handler's 401 check.

Fix: the no-tenant tests now patch settings with an empty cosmos_db_endpoint, which triggers the dev-mode-no-cosmos path in the middleware (sets tenant=None and passes through). All 144 tests pass.