feat: show error messages on 500 pages when connected

Is your feature request related to a problem? Please describe

500 pages are too confusing, and it should be the case for anonymous visitors (for security reasons). Nevertheless, it impedes on the communication when trying to debug the problem for developers.

Describe the solution you'd like

When connected and facing the 500 error, users should be able to understand how to proceed next to debug the error. The page should display the error message without the stack trace on the 500 page + a message stating what they could do next.

--> ie. "Found a bug? Create a new issue [with link] or go to the Castopod chat to get help!"

Describe alternatives you've considered

Users may also be prompted to go to their writable/logs/ folder and copy/paste their logs OR have a button to copy the error's stack trace directly!

Additional context

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