T1: Identity domain entities + service interface

[devin-ai-integration]

Summary

Adds the domain layer for the Identity microservice — plain C# entities, DTOs, and a service interface. No ASP.NET Identity or OpenIddict dependencies.

Entities (Identity.Domain.Entities):

• AppUser — user profile with PasswordHash, IsEnabled, timestamps
• AppRole — simple id/name/description role

DTOs (Identity.Domain.DTOs):

• RegisterRequest / RegisterResult
• LoginRequest / LoginResult
• AppUserDto (projection without sensitive fields)

Interface (Identity.Domain.Interfaces):

public interface IIdentityService
{
    Task<RegisterResult> RegisterAsync(RegisterRequest request);
    Task<LoginResult> LoginAsync(LoginRequest request);
    Task<AppUserDto?> GetUserByIdAsync(Guid id);
    Task<IEnumerable<AppUserDto>> GetAllUsersAsync();
}

Build passes: dotnet build Services/Identity/Identity.API/Identity.API.csproj -c Release
No forbidden symbols (IdentityUser, IdentityRole, OpenIddict, ApplicationDbContext, QuickApp.Core.Models.Shop) present.

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/0f07b7a8f1014aec962930431c54da9f
Requested by: @mbatchelor81

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.