[FEAT] Store fused Pokémon as combined data (preserve both fusion parts)

[Myldym]

Is your feature request related to a problem?

Yes. Currently, when storing fused Pokémon (e.g. Dusk Mane Necrozma), only the main Pokémon is saved — in this case, only Necrozma. This is because of how fusion mechanics are structured in the games.
However, this could potentially cause issues when transferring to another game where the fusion might need to be separated, since the second part of the fusion (e.g. Solgaleo or Lunala) isn’t stored.

Describe the solution you'd like

Add an option or system that allows fused Pokémon to be stored with both fusion components preserved.
For example:

• Dusk Mane Necrozma → Necrozma + Solgaleo (both saved internally).

• When transferred or unfused later, both parts can be restored correctly.

Additional context

Not sure if technically possible, but it would be helpful for preserving full fusion data across different games and preventing potential transfer errors or data inconsistencies.
If this is impossible, I think the best solution would be to block the transfer of fused Pokémon, similar to how it works in the official Pokémon HOME.