[server] Provide more information about the problem

[michaelfromyeg]

The /problems endpoint should provide more information, such as:

• An more suitable title
• A source URL
• Test cases in nice-ish formatting (this will be hard)
• Context / reference links / hints (its aimed at beginners, so hints are important)

[michaelfromyeg]

I could probably insert a hint bit with LLMs? Maybe a premium version of the endpoint.