SS-1854 expand gpu support

[hamzaimran08]

Description

This PR relates to SS-1854 and SS-1936.

It expands GPU support across app types and adds a capacity check before GPU-backed apps are created.

• Enables GPU-capable flavors for more app templates, including RStudio, VS Code, Dash, Gradio, and Streamlit, when the app template is marked gpu_enabled.
• Adds GPU capacity chekcs based on active database app instances and the selected flavor’s gpu_req.
• Disables GPU flavors in the app form when unavailable and validates the selection on submit.
• Adds a locked capacity check before saving an app, so concurrent requests cannot both claim the last available GPU.
• Shortens cleanup for Develop apps that hold a GPU from 7 days to 1 day, while leaving non-GPU Develop apps at 7 days.
• Adds GPU_TOTAL_CAPACITY configuration with a default of 0.

Checklist

• This pull request is against develop branch (not applicable for hotfixes)
• I have included a link to the issue on GitHub or JIRA (if any)
• I have included migration files (if there are changes to the model classes)
• I have added or updated unit and end2end tests or a manual test case to complement my changes
• I have ran unit and end2end tests
• I have updated the related documentation (if necessary)
• I have added a reviewer for this pull request
• I have added myself as an author for this pull request
• In the case I have modified settings.py, then I have also updated the studio-settings-configmap.yaml file in serve-charts
• In case your changes are large enough, did you deploy your changes to develop instance?

[akochari]

I know this is not part of this Jira ticket but perhaps good to do here anyway: can you please also add GPUs in the flavor addition menu in project settings? settings/?tab=flavors

[akochari]

Another unrelated but quite important thing now that we will have instances that can be deleted within 24 hours:
We need to add some info about when the particular app in the Develop category will be deleted. Maybe simple countdown with JS given that we have the date created right there? E.g. 5 days remaining, 20 hours remaining? Or only display it once it's less than 24 hours? Or any other solution to indicate that this instance will be deleted.
But also, given that we do not delete immediately but at some point during the night maybe when it expires it should say something like "scheduled for deletion"?