Loading Data: fall-back to KEF

[jdlcdl]

DRAFT: For a future release AFTER v25.09.0

What is this PR for?

Focus of this PR is to re-prioritize loading of data (scanned or from sd) to be treated as plaintext, within context, instead of first attempting to parse and decrypt a KEF envelope. PSBTs in particular, which are often loaded in binary, form can appear to be KEF, but if they can be parsed as PSBTs first, then user will not have to answer "No". If parsing fails, in this case -- as a PSBT, we could then fall-back to see if it was KEF, and try again after decryption.

Loading of datum-types TO DO:

• [x] addresses
• [x] descriptors
• [ ] messages to be signed
• [ ] PSBTs

In some cases, this is not possible, a KEF must be checked first, in cases where data is treated as random bytes and no other obvious parsing could be done... ie) for mnemonic entropy, passphrases, and for decryption keys we should check if it's a KEF first (rather than treating 32 bytes as a mnemonic, or base43 text as a passphrase, or a string of bytes as the decryption key when in fact these would normally parse as kef envelopes to prompt decryption... and in the case of a false-KEF the user will know NOT to decrypt.

In most other cases, we could try to parse in plaintext form first, and then fall back to trying KEF if it fails.

Changes made to:

• [x] Code
• [x] Tests
• [x] Docs
• [ ] CHANGELOG

Did you build the code and tested on device?

• [ ] Yes

What is the purpose of this pull request?

• [ ] Bug fix
• [ ] New feature
• [ ] Docs update
• [x] Other

[codecov[bot]]

Codecov Report

:x: Patch coverage is 96.72131% with 2 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 96.64%. Comparing base (8673400) to head (0bdf481).

Files with missing lines	Patch %	Lines
src/krux/pages/home_pages/wallet_descriptor.py	94.28%	2 Missing :warning:

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #702   +/-   ##
========================================
  Coverage    96.64%   96.64%           
========================================
  Files           79       79           
  Lines        10150    10176   +26     
========================================
+ Hits          9809     9835   +26     
  Misses         341      341           

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