Update dependency pydantic to v2.11.4

Author: renovate[bot]

backend/requirements.txt

@@ -8,7 +8,7 @@ imblearn==0.0
 matplotlib==3.10.0
 mutagen==1.47.0
 openai==1.61.1
-pydantic==2.10.4
+pydantic==2.11.4
 pydantic-settings==2.8.0
 plotly==6.0.0
 pyAudioAnalysis==0.3.14