Add Permission Requests for joining the LeetCode Leaderboard

[adarshm11]

sign2's ssh tunneling will need to be fixed before #1981 is merged before we do this so bruh someone do something abt those please

inspired by the permission requests for the led sign, we should allow users to make requests to join the sce leetcode leaderboard! right now there's a QR code for signups on a google form that export to a google sheet and people who apply just wait for someone to manually add them and there's no one looking at allat 🦗

so let's just let them be more direct! it's much easier for someone to just go on clark and approve/deny these things

• we need to add a new schema to store leaderboard permission requests. refer to /api/main_endpoints/models/PermissionRequest.js for the led sign implementation
• then we need to create an api for managing leaderboard permission requests. we should have an endpoint to store a new request, and an endpoint to approve/deny a request
• next we need a new component on the frontend where, on the leaderboard page, officers can see users who applied and approve/deny their requests. that would call the endpoint to approve/deny obv
• finally once requests are approved they'll need to be posted to the sign2's server with the appropriate setup. refer to sign2 source code for that implementation

idea: what if there's a way to verify if a leetcode profile exists? some of these jits have made typos in their leetcode profile so we don't wanna force officers to manually check the profiles on leetcode (if possible). could we check https://leetcode.com/u/{username} to see if that profile exists, and auto delete requests made with profiles that don't exist? does leetcode allow that? experiment with ts!