Refactor: Remove NFStream and flow identity utilities; introduce Tshark manager

- Deleted flow_identity.py and nfstream_flow_worker.py as they are no longer needed.
- Removed nfstream_manager.py and its associated logic for managing NFStream workers.
- Added tshark_manager.py to manage tshark packet enrichment and matching.
- Updated setup_build_server.sh to include default environment variables for tshark.
- Implemented packet signature generation and enrichment logic in the new TsharkManager class.

backend/Dockerfile

@@ -3,7 +3,7 @@ FROM python:3.11-slim
 WORKDIR /app
 
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends build-essential libpcap-dev pkg-config \
+    && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends build-essential libpcap-dev pkg-config tshark \
     && rm -rf /var/lib/apt/lists/*
 
 COPY requirements.txt .