perf: reduce Gunicorn workers to 1 for stability

- Change from 4 workers to 1 worker in both Dockerfile and docker-compose.yml
- Helps reduce resource usage and connection reset issues
- Better for single-user or low-traffic deployment scenarios

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Dockerfile

@@ -32,7 +32,7 @@ RUN uv venv && \
 ENV FLASK_APP=main.py
 ENV FLASK_ENV=production
 ENV PATH="/app/.venv/bin:$PATH"
-ENV GUNICORN_CMD_ARGS="--workers=4 --bind=0.0.0.0:5000 --timeout=120"
+ENV GUNICORN_CMD_ARGS="--workers=1 --bind=0.0.0.0:5000 --timeout=120"
 
 # Expose port
 EXPOSE 5000