feat: add MasterPasswordSalt column to User table
- Add MasterPasswordSalt column to User table in both Dapper and EF implementations
- Update User stored procedures (Create, Update, UpdateMasterPassword) to handle salt column
- Add EF migrations and update UserView with dependent views
- Set MaxLength constraint on MasterPasswordSalt column
- Update UserRepository implementations to manage salt field
- Add comprehensive test coverage for salt handling and normalization
