Add report deduplication and single-report deletion

Agent-Logs-Url: https://github.com/christianlouis/dmarq/sessions/37d68c2c-7cc8-45e4-bac3-e2e6f1611c6a

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

backend/app/tests/test_reports_api.py

@@ -69,3 +69,66 @@ def test_upload_and_get_domain_summary(client: TestClient):
     assert data["domain"] == "example.com"
     assert data["total_count"] == 2
     assert data["reports_processed"] == 1
+
+
+def test_duplicate_upload_returns_409(client: TestClient):
+    """Uploading the same report twice returns 409 Conflict."""
+    zip_bytes = _make_zip(SAMPLE_XML)
+
+    first = client.post(
+        "/api/v1/reports/upload",
+        files={"file": ("report.zip", zip_bytes, "application/zip")},
+    )
+    assert first.status_code == 200
+
+    second = client.post(
+        "/api/v1/reports/upload",
+        files={"file": ("report.zip", zip_bytes, "application/zip")},
+    )
+    assert second.status_code == 409
+    assert "already been uploaded" in second.json()["detail"].lower()
+
+
+def test_delete_report_success(client: TestClient):
+    """Deleting an existing report returns 200 and removes it from the store."""
+    zip_bytes = _make_zip(SAMPLE_XML)
+    client.post(
+        "/api/v1/reports/upload",
+        files={"file": ("report.zip", zip_bytes, "application/zip")},
+    )
+
+    # Confirm the domain exists first
+    assert client.get("/api/v1/reports/domain/example.com/summary").status_code == 200
+
+    # Delete the report (report_id comes from SAMPLE_XML: "123456789")
+    response = client.delete("/api/v1/reports/domain/example.com/reports/123456789")
+    assert response.status_code == 200
+    data = response.json()
+    assert data["success"] is True
+
+    # Domain should be gone now
+    assert client.get("/api/v1/reports/domain/example.com/summary").status_code == 404
+
+
+def test_delete_nonexistent_report_returns_404(client: TestClient):
+    """Deleting a report that does not exist returns 404."""
+    response = client.delete("/api/v1/reports/domain/example.com/reports/no-such-id")
+    assert response.status_code == 404
+
+
+def test_upload_after_delete_succeeds(client: TestClient):
+    """After deleting a report, the same report can be uploaded again."""
+    zip_bytes = _make_zip(SAMPLE_XML)
+
+    client.post(
+        "/api/v1/reports/upload",
+        files={"file": ("report.zip", zip_bytes, "application/zip")},
+    )
+    client.delete("/api/v1/reports/domain/example.com/reports/123456789")
+
+    response = client.post(
+        "/api/v1/reports/upload",
+        files={"file": ("report.zip", zip_bytes, "application/zip")},
+    )
+    assert response.status_code == 200
+    assert response.json()["success"] is True