chore: point fideslang to branch with data_purposes support

Update fideslang dependency to use the feat/add-data-purposes-to-dataset-models
branch which adds data_purposes at dataset, collection, field, and sub-field
levels.

Dependency: ethyca/fideslang#39

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Adrian Galvan

pyproject.toml

@@ -56,7 +56,7 @@ dependencies = [
     "fastapi-cli~=0.0.16",
     "fastapi-pagination[sqlalchemy]==0.15.0",
     "fastapi[all]==0.123.3",
-    "fideslang==3.1.4a1",
+    "fideslang @ git+https://github.com/ethyca/fideslang.git@feat/add-data-purposes-to-dataset-models",
     "fideslog==1.2.15",
     "firebase-admin==5.3.0",
     "flower==2.0.1",