- Add Fengling.Platform domain and infrastructure projects
- Move Tenant aggregate from AuthService/Console to Platform.Domain
- Add TenantRepository and SeedData to Platform
- Remove duplicate Tenant/TenantInfo models from AuthService and Console
- Update controllers and services to use Platform.Domain.Tenant
- Add new migrations for PlatformDbContext
BREAKING CHANGE: Tenant entity now uses strongly-typed ID (TenantId)
