refactor: remove unused parameters and variables

- Remove unused `useRouter` import in `auth.ts`
- Update `verifyUserDoesntExists.ts` and `verifyUserExists.ts` to remove
  unused `to` parameter
- Remove unused `to` parameter in `verifyUserExists.ts`
- Eliminate unused `generatedSession` variable in `login.ts`
- Simplify handler function in `userExists.ts` by removing `event` param

middleware/verifyUserDoesntExists.ts

-export default defineNuxtRouteMiddleware(async (to) => {
+export default defineNuxtRouteMiddleware(async () => {
     if (process.env.NODE_ENV === 'development') {
         return;
     }

middleware/verifyUserExists.ts

-export default defineNuxtRouteMiddleware(async (to) => {
+export default defineNuxtRouteMiddleware(async () => {
     if (process.env.NODE_ENV === 'development') {
         return;
     }

server/api/auth/login.ts

@@ -19,7 +19,7 @@ export default defineEventHandler(async (event: H3Event<EventHandlerRequest>) =>
         throw createError({statusCode: 401, statusMessage: 'Invalid credentials'});
     }
 
-    const generatedSession = await generateSession(user, event);
+    await generateSession(user, event);
 
     return {
         id: user.id,

server/api/auth/userExists.ts

 import prisma from "~/lib/prisma";
 
-export default defineEventHandler(async (event) => {
+export default defineEventHandler(async () => {
     const userCount = await prisma.user.count();
     return { userExists: userCount > 0 };
 })
\ No newline at end of file

stores/auth.ts

 import { defineStore } from 'pinia';
-import { useRouter } from 'vue-router';
 
 export const useAuthStore = defineStore('auth', {
     state: () => ({