Default self-contained system for product development

[tjementum]

A major architectural restructure introducing a new "main" self-contained system as the default SCS and host of module federation, while renaming account-management to account and reorganizing navigation to create a seamless single-page application experience across all SCSs.

Overview

• Main SCS: New default self-contained system that serves as the catch-all route in YARP, hosts module federation, owns the landing page (/) and home dashboard (/home), and provides the primary app layout
• Account SCS: Renamed from account-management, moves from /admin/* to /account/*, becomes a federated module consumed by main SCS
• Navigation restructure: Replace the current top menu + side menu pattern with a single AccountMenu dropdown in the top-left corner that consolidates account switching, user profile, language, theme, support, sessions, and logout
• True SPA experience: No full page reloads when navigating between SCSs - achieved through module federation where main SCS is the host and account SCS is a remote
• Back-office isolation: Remains completely standalone without any federation - remove current AvatarButton federation usage

[linear]

PP-877