Migrate from User to Account domain concept

Renames core domain entities and services from "User" to "Account"

Refactors project-wide namespaces, classes, and database tables to use "Account" terminology
Updates related components, services, and database schema to reflect new domain naming
Standardizes naming conventions across authentication and organization setup features

PlanTempus.Components/CommandHandler.cs

@@ -1,5 +1,4 @@
 using Autofac;
-using PlanTempus.Components.Users.Create;
 using PlanTempus.Core.CommandQueries;
 
 namespace PlanTempus.Components;