Add support for Add to shortcut

[TimoPtr]

We've introduced Add to feature in https://github.com/home-assistant/android/pull/5622 and it would be nice to extend it to Shortcut.

The UI for selecting an action is available starting from HA core 2025.12.0 or (in nightly/dev).

• we need to adjust the logic of EntityAddToHandler to only enable the shortcut option if we have a shortcut left to fill (current max is 5) otherwise it should be shown but marked as disabled.
• we need to adjust the ManageShortcutsSettingsFragment to be able to take a parameter the entity ID selected and put it into the next available slot

In this task you will also have to update the unit tests in EntityAddToHandler

[ujjol1234]

@TimoPtr can I work on this

[TimoPtr]

@TimoPtr can I work on this

Not yet unfortunately I need to finish the frontend part.

[TimoPtr]

This can be worked on since the PR on the frontend and android have been merged.