feat: enhance firefox 144+ master key retrieval and improve padding validation

[Aquilao]

Proposed changes

PR #498 missed a scenario where multiple candidate keys would cause an error in Firefox, preventing password decryption. While the cause of multiple candidate keys is currently unknown, this issue occurred on both my test machine and my work PC.

This problem has now been fixed, and the code robustness has been improved.

I tested it with versions 143 (one candidate key), 144 (one candidate key), and 148 (two candidate keys), and the code runs correctly.

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit, build tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[moonD4rk]

LGTM, Great Job!