fix: ensure config and data directories exist with proper permissions in Docker container

- Create /usr/src/app/config and /usr/src/app/data directories before setting ownership
- Fixes permission issues when saving configuration via web UI
- Resolves issue #109 where appuser cannot write to .env file in mounted config volume

Dockerfile

@@ -43,6 +43,9 @@ COPY --from=builder /usr/src/app/package.json ./
 # Optionally copy other root files if needed by the application (e.g., .env.example, README)
 # COPY --from=builder /usr/src/app/.env.example ./
 
+# Create config directory for persistent volume mount and data directory
+RUN mkdir -p /usr/src/app/config /usr/src/app/data
+
 # Ensure correct ownership of application files
 # Use /usr/src/app to cover everything copied
 RUN chown -R appuser:appgroup /usr/src/app