fix(ui): fix UI behavior in no namespace state

[luizhf42]

This pull request focuses on improving the user experience when no namespaces exist and refactors related UI logic to be more consistent and maintainable. The changes clarify the flow for users who have not yet created or joined a namespace, streamline the display of dialogs and buttons, and ensure that UI components are properly enabled or disabled based on namespace availability.

• The Home view (Home.vue) now clearly distinguishes between users with and without namespaces, providing a prominent call-to-action to create a namespace and a detailed description of namespaces for new users. The logic for error handling and state tracking has also been simplified.
• The namespace instructions dialog was fixed to be closeable, not locking the user if he doesn't have a namespace, allowing actions like profile editing and logout.
• The "Quick Connect" button is now disabled when no namespaces exist, and its logic has been updated to prevent opening the dialog or using keyboard shortcuts in this state.
• The "Add Namespace" button and dialog have been removed from the navigation drawer.

These changes collectively enhance the onboarding experience for new users, clarify the UI state when namespaces are not present, and improve code maintainability.