feat: add user and leaderboard service

spec.json

src/api/index.ts

src/api/models/LeaderboardDTO.ts

src/api/models/LeaderboardEntryDTO.ts

src/api/models/ProfileDTO.ts

src/api/models/SignUpRequest.ts

src/api/models/UserDTO.ts

src/api/models/UserUpdateDTO.ts

src/api/services/LeaderboardService.ts

src/api/services/UserControllerService.ts