Refactor Dockerfile for optimized build

Simplified the Dockerfile in the backend component by streamlining Python and system dependencies installation. Upgraded to Python 3.11 and ensured only necessary packages are installed, reducing image size and potential security vulnerabilities. Unused package lists are removed to maintain a clean build environment.

Dockerfile

@@ -53,20 +53,16 @@ ENV SENTENCE_TRANSFORMERS_HOME $RAG_EMBEDDING_MODEL_DIR
 
 WORKDIR /app/backend
 
-# install python dependencies
+# install python & dependencies
 COPY ./backend/requirements.txt ./requirements.txt
 
-RUN apt-get update && apt-get install ffmpeg libsm6 libxext6  -y
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends python3.11 ffmpeg libsm6 libxext6 pandoc netcat-openbsd && \
+    rm -rf /var/lib/apt/lists/*
 
 RUN pip3 install torch torchvision torchaudio --no-cache-dir
 RUN pip3 install -r requirements.txt --no-cache-dir
 
-# Install pandoc and netcat
-# RUN python -c "import pypandoc; pypandoc.download_pandoc()"
-RUN apt-get update \
-    && apt-get install -y pandoc netcat-openbsd \
-    && rm -rf /var/lib/apt/lists/*
-
 # preload embedding model
 RUN python -c "import os; from chromadb.utils import embedding_functions; sentence_transformer_ef = embedding_functions.SentenceTransformerEmbeddingFunction(model_name=os.environ['RAG_EMBEDDING_MODEL'], device=os.environ['RAG_EMBEDDING_MODEL_DEVICE_TYPE'])"
 # preload tts model