Update python task templates only when python models exist.

[ajayjayendran]

• source_etl uses a Python-aware template only when Python models exist. When dj.airflowGenerateDags is enabled, DJ always writes a single source_etl.py DAG (dag_id source_etl). Without Python models it copies the no-Python source_etl.py template;

[arunxdev]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.