fix(cryptography): verify public key matches private key in BasicCredential::from_raw

[Sertug17]

Closes #3799

Add a verification step after constructing the SigningKey to ensure
the caller-supplied public key corresponds to the private key.
Previously, (private_key_A, public_key_B) pairs were accepted,
enabling signature forgery where an attacker could sign with their own
key but claim a victim's public key.

Note

Verify public key matches private key in BasicCredential::from_raw

• Adds validation in BasicCredential::from_raw to reject mismatched private/public key pairs, confirmed by a new test in basic_credential.rs.
• Updates browser SDK tests to replace fixed sleep() delays with polling via waitFor, reducing timing-related flakiness in device sync and preferences tests.
• Extends the waitFor helper in helpers.ts to support async predicates by awaiting the condition on each poll iteration.

^{Macroscope summarized a6d4cd3.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.69%. Comparing base (7a0f50f) to head (a6d4cd3).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3801      +/-   ##
==========================================
+ Coverage   84.54%   84.69%   +0.15%     
==========================================
  Files         410      409       -1     
  Lines       60716    60902     +186     
==========================================
+ Hits        51331    51583     +252     
+ Misses       9385     9319      -66     

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