fix: use absolute import for nl_to_sparql in function_app.py

Relative imports (from .nl_to_sparql) fail in Azure Functions v2
because the api/ directory is not treated as a Python package.
The function app root is added to sys.path, so absolute imports work.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: lqdev

api/function_app.py

@@ -14,7 +14,7 @@
 import rdflib
 from rdflib import Dataset, Graph
 
-from .nl_to_sparql import translate, validate_sparql, enforce_safety
+from nl_to_sparql import translate, validate_sparql, enforce_safety
 
 app = func.FunctionApp(http_auth_level=func.AuthLevel.ANONYMOUS)