Add EMBG property and consolidate migrations
Added EMBG property to User and RegisterDto classes to store unique user identifiers. Removed outdated migration files and introduced a new consolidated migration (20251029131316_InitialCreate) to define the database schema, including User, ContactInfo, EnrollmentInfo, HighSchool, and RefreshToken tables with appropriate relationships. Updated AppDbContextModelSnapshot to reflect the new schema. Changed the development database connection string in appsettings.Development.json for improved configuration.
