refactor: ui separation from controller

[Tbaile]

• Standalone bundle can now be served directly by a unit proxied at /<uuid>/ behind a controller, instead of always going through the controller's legacy embedded route — deployment
  location (unit / proxied unit / controller-embedded) is derived from the document path and build mode via a new lib/deployment.ts, replacing the old isStandaloneMode flag. Units
  advertise support via ui_version; older units keep the legacy path
• API endpoints, localStorage keys, and user preferences are now scoped per deployment (lib/config.ts, new lib/storage.ts), so multiple proxied unit UIs sharing the controller's
  origin no longer collide on session, remembered username, or preferences
• Static assets (logos, favicon, branding.js) moved from public/ into the compiled bundle and referenced relatively (vite.config.ts base ./, %BASE_URL%), fixing asset and API
  paths that broke when the UI is served under a controller's path prefix instead of the origin root
• Proxied unit whose session expired now sends the operator back to the controller instead of showing a login form it can't use, since the unit's credentials live in the controller, not
  the unit itself
• Added an "installed packages" list to the system update page

TODO: Check if RebootAndShutdownView.vue's availability-poll approach actually works when the unit is managed by a controller
TODO: Remove InstalledPackagesModal.vue's when testing is done, is used just to check if the UI gets proxied correctly

Closes: NethServer/nethsecurity#1893