Display logged-in banner on homepage (#2742)

* Display logged-in banner on homepage

Pass auth_user from the router into PuterHomepageService and show a logged-in banner when a user is present. _default.js now includes auth_user in the svc_puterHomepage.send call. PuterHomepageService.send signature was updated to accept auth_user; the service stores logged_in_user, forwards it to generate_puter_page_html, and injects a styled "Logged in as <username>" banner into the top of the page when available. This surfaces the current user on the GUI and exposes logged_in_user to page generation and addons.

* Include request path and logged in user in GUI params; remove banner

* fix: bad auth_user check for homepage

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Co-authored-by: Daniel Salazar <daniel.salazar@puter.com>