[Feature] Add possibility to add additional custom obects from Typed-tab

[sepetuks]

Problem description

Better usability for user experience

Proposed solution

Be able to link custom objects (from objects type) using Typed-Tab on specific app model.

Alternatives considered

Yes using natively from Custom Objects menu is possible

Additional context

I have custom object type that allows multiobject linking of Custom Object type Objects.

It would be very nice to be able to link additional ones (Product names) from appmodel side (in this case from VM or Device view)

Not only editing it via Custom Objects menu:

[Kani999]

Proposed in #10.

Behavior: each Typed tab gets an "Add Type" button (top-right). Clicking it opens the native customobject_add view with the back-reference field pre-populated to the parent object's PK and return_url set to the tab path, so saving lands you back on the tab with filters preserved.

Multi-field case: if a Custom Object Type has more than one field referencing the same parent model (e.g. primary_device + backup_device → Device), the button becomes a split-dropdown listing each field.

Permissions: hidden for users lacking add_customobject.

Note on empty tabs: typed tabs still use hide_if_empty=True — the tab is only visible once at least one object references the parent, so the first instance still needs to be created via the native Custom Objects menu. Subsequent additions use the new button. Open to switching to "always visible when user can add" if that's preferred.