feat: add fuse-overlayfs storage driver for Docker-in-Docker

- Install fuse-overlayfs package in Dockerfile
- Configure Docker daemon to use fuse-overlayfs storage driver
- Add daemon.json configuration in entrypoint.sh
- Update documentation in README.md and README.es.md

This enables Docker-in-Docker to work efficiently in unprivileged
containers without requiring the overlay2 driver.

README.md

@@ -5,7 +5,7 @@ A developer container powered by [code-server](https://github.com/coder/code-ser
 ## Features
 
 - 💻 code-server (VS Code in the browser)
-- 🐳 Docker-in-Docker (DinD)
+- 🐳 Docker-in-Docker (DinD) with fuse-overlayfs storage driver
 - 🔐 Password or hashed password auth via `.env`
 - 👤 Dynamic user configuration (UID, GID, password)
 - ⚙️ Preinstalled: Docker, AWS CLI v2, kubectl, eksctl, Node.js, Python, Java, pre-commit, etc.
@@ -60,7 +60,7 @@ Login using the credentials defined in `.env`.
 
 ## Tooling Included
 
-- Docker CLI
+- Docker CLI (with fuse-overlayfs storage driver for unprivileged containers)
 - AWS CLI v2
 - kubectl (`v1.33.0`)
 - eksctl
@@ -70,6 +70,10 @@ Login using the credentials defined in `.env`.
 - pre-commit
 - siege, jq, git, etc.
 
+## Docker Storage Driver
+
+This container uses `fuse-overlayfs` as the Docker storage driver, which allows Docker-in-Docker to work efficiently in unprivileged containers without requiring the `overlay2` driver. The configuration is automatically set in `/etc/docker/daemon.json` during container startup.
+
 ## Clean Up
 
 ```bash