Docker: remove tf-keras, keep native keras 3

Dockerfile

@@ -9,9 +9,7 @@ RUN pip install --no-cache-dir fastapi==0.111.0 uvicorn==0.30.1 pydantic==2.7.4
     pydantic-settings==2.3.4 numpy==1.26.4 pandas==2.2.2 scikit-learn==1.3.2 \
     scipy==1.13.1 nltk==3.8.1 tensorflow==2.16.1 keras==3.3.3 \
     transformers==4.41.2 joblib==1.4.2 && \
-    pip install --no-cache-dir torch==2.3.1 --index-url https://download.pytorch.org/whl/cpu && \
-    pip install --no-cache-dir tf-keras && \
-    python -c "import tf_keras; print('tf-keras OK')"
+    pip install --no-cache-dir torch==2.3.1 --index-url https://download.pytorch.org/whl/cpu
 
 RUN python -c "import nltk; nltk.download('stopwords', quiet=True); nltk.download('punkt', quiet=True); nltk.download('wordnet', quiet=True)"