Adopt and migrate according to Kolibri’s new app hooks in kolibri-app

[ozer550]

Description

Kolibri PR #12879 deletes the legacy kolibri.plugins.app plugin and replaces it with hook-based capabilities (GetOSUserHook, CheckIsMeteredHook, ShareFileHook).

Wrapper in kolibri-app still depends on the removed plugin, so it can no longer launch or expose app-only features when running against the PR mentioned above. To stay compatible with current and future Kolibri releases, we must migrate to the new hook architecture.

Current Behaviour

• Following files application.py, server_manager_posix.py, and server_process_windows.py import kolibri plugins app interface, register it and builds initialization URLs.
• KolibriApp’s kolibri_plugin.py does not implement any of the new core hooks, so capabilities such as OS user login, metered-connection checks, file sharing plugins are never registered.
• We register the old app plugin and have a dependency on it.

Desired Behaviour

1. kolibri_app/kolibri_plugin.py registers concrete implementations of the new hooks:
   • GetOSUserHook → Return a fixed desktop pseudo-user so Kolibri can auto-login when the app launches (e.g., ("KolibriDesktopUser", True)). Otherwise return (None, False). eg: here.
   • CheckIsMeteredHook → Return True if the OS reports a metered connection, else False. If the platform can’t detect this, just return False. eg: here.
   • ShareFileHook → Implement share_file(self, filename, message) so the desktop wrapper hands that file off to the OS sharing UX (reveal/open in Explorer/Finder or show a native share dialog). Ensure the hook checks that the file exists, logs failures, and replaces the old no-op share_file = None/interface.register_capabilities code so Kolibri’s “Share” button works again.
2. Replace importing kolibri.plugins.app.utils and instead call app_initialize_url() from kolibri.core.device.utils to construct initialization URL.
3. All enable_plugin("kolibri.plugins.app") calls are removed.
4. Any previous interface.register( ) blocks are deleted, the hook registrations in kolibri_plugin.py handle capability wiring automatically.
5. Windows/Posix server managers rely solely on hook side effects (no manual registration).

Reference

• Look into this PR.
• Hooks implementation examples here.