Update Dockerfile and add devcontainer support

[MhhhxX]

I updated the Dockerfile to ubuntu 24.04 and Nextcloud 31.

Devcontainer support:

I added support to develop passman inside a devcontainer with vscodium.
Usage:

1. Install the DevPod Containers extension in VSCodium and activate the experimental api for this extension
2. Install the devpod cli.
3. Configure devpod provider with devpod provider add docker and devpod provider use docker
4. F1 -> Devpod Containers: Open in Container
5. Open localhost:3001 in your browser for auto reload when js files changes or localhost:9001 for the regular site.

[binsky08]

thanks so much, looks very good :)