ci: switch Dependabot from pip to uv ecosystem for proper uv.lock updates (#168)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: aaronsteers

.github/dependabot.yml

@@ -33,8 +33,8 @@ updates:
       - dependencies
       - github-actions
 
-  # Python dependencies (uv / pyproject.toml)
-  - package-ecosystem: pip
+  # Python dependencies (uv / pyproject.toml + uv.lock)
+  - package-ecosystem: uv
     directory: /
     schedule:
       interval: weekly