feat: add phone field to User model and update authentication flow

- Added phone field to User model in Prisma schema and generated types.
- Updated backend authentication to include phone as an additional field.
- Implemented phone input in the signup form with validation.
- Created a new SignupPage component for user registration.
- Updated routing to include signup path and redirect authenticated users.
- Modified login page to reference Playzer and added link to signup.

apps/backend/prisma/migrations/20260601193348_add_phone_to_user/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "users" ADD COLUMN     "phone" TEXT;