Update dependency markdown to v3.9

Author: renovate[bot]

requirements.txt

@@ -12,7 +12,7 @@ requests==2.32.4
 python-dotenv==1.1.0
 alembic==1.15.2
 boto3==1.38.20
-markdown==3.8.0
+markdown==3.9
 email-validator==2.1.2
 prometheus-client==0.21.1
 prometheus-fastapi-instrumentator==7.0.0