Refactor Dockerfile to use entrypoint script, update requirements for bcrypt, and enhance FastAPI app with optional user retrieval and improved error handling

docker-entrypoint.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+set -e
+mkdir -p /app/data
+chown -R appuser:appgroup /app/data
+exec runuser -u appuser -- uvicorn app.main:app --host 0.0.0.0 --port 8000