fix: validate types for login email and password (500 on non-string or missing body) #235

Summary

userLoginController (apps/http-server/src/controllers/authController.ts) is the one auth input that is still only checked for being truthy. Register has parseRegisterInput, and join and create quiz got the same treatment in #231, but login still does const { email, password } = req.body and if (!email || !password).

What happens

From reading the code, POST /api/v1/auth/login should give a generic 500 in these cases:

• No JSON body: the destructure throws, same as the no body case that fix(http-server): validate types and lengths for join and create quiz input #234 fixed for join.
• {"email":{},"password":"x"}: gets past the check, then Prisma throws a validation error in findUnique.
• {"email":"real@user.com","password":123}: bcrypt.compare throws on a non string.

I didn't run these against a database, the join versions behaved this way when I tested #234.

Expected behaviour

400 with a clear message for wrong types.

Proposed fix

A small parseLoginInput next to registerInput.ts, returned through the existing errorResponse(res, 400, ...), with tests for the object, array, number and no body cases.

Happy to send a PR for this, and #234 is merged so I don't have anything else open here. Labels and level are your call.