feat: use official templates from sandbox-templates

[alexnm]

Core feature has been implemented:

• devbox templates are fetched from github (json file)
• sandbox templates are fetched from the old /official endpoint

Still to decide:

• what categories we show for devboxes, based on the tags
• should we order templates based on some priority or is it ok to show them in alphabetic order or based on number of forks?
• project starters

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