Join server errors on invite codes with slashes

The join server input should handle invite codes containing forward slashes gracefully, including full invite URLs like https://flackle.com/invite/IDOALYJH. Currently, any input where the invite code is separated by "/" characters returns an internal server error, while the same input without slashes returns a proper "Invalid invite" message. The join flow should strip or parse surrounding URL parts and delimiters instead of failing with a server error.

Example
when joining a server with a link:

https://flackle.com/invite/IDOALYJH

if the entire URL is pasted into the join, it’ll read as an internal server error.

it’ll also read as an internal server error as long as the invite code is separated by a “/”

for example:

this reads an internal server error due to the forward slash. if the forward slash is removed:

this bug also works with the forward slash being behind the invite code. so, as long as the invite code is separated by “/”, the code will work.