feat: broadcast transaction

[r1b2ns]

It adds support for broadcasting transactions using the active unsealed slot.

This PR only adds the broadcast functionality. In the next PR, I plan to propose improvements to the sats spending layout.

Evidence
https://drive.google.com/drive/folders/15WbHl6C8QdMslhFajTsN-V7N_cYlOoGI?usp=share_link

[reez]

WOOT!!! Will review

[reez]

Deep review done.

First off: this is a huge feature and cool that you made successful sends. The happy path is clearly working.

I left comments on a few things

Would like to fix before merge (but open to merging even without):

1. Post success NFC invalidation can overwrite the success state/message after broadcast (.done isn’t treated as a terminal success state in the invalidation handler).
2. dump(slot:) -> unseal(cvc:) fallback can unseal the wrong slot when sweeping an inactive slot, because unseal(cvc:) is active-slot only.

Follow-up OK (non-blocking):

1. “Sweep balance” button state can stay disabled in one fallback path (tx fetch fails but balance fetch succeeds).
2. Slot row label says “Card ID” while copying/displaying the slot address.

But im totally flexible on how we do this, I can make the changes myself on this pr, or do the follow ups myself? Feel free to let me know what you think makes things easiest.

The goal is to get this merged soon and not hold you up or do multiple rounds of reviews that slow this down, and make it an easy process.

[r1b2ns]

Thanks for the review, @reez ! I just pushed a new commit fixing these issues.

[reez]

ACK f38a859

HUGE thank you @r1b2ns