Adds AuthContext with Orval API integration, user login/logout/register flows, and account settings page. Refactors navigation and layouts to use authentication context. Introduces new account-related pages (Login, Register, Logout, AccountSettings), updates PrivateRoute to use AuthContext, and improves error handling in Downloader. Removes obsolete context example and adds comprehensive usage documentation for AuthContext.
Expanded chat backend with message reply, edit, delete, and reaction support in consumers and models. Updated routing to use chat_id. Added chat-related view stubs. On the frontend, introduced ChatLayout and ChatPage scaffolding, and routed protected routes through ChatLayout.
