Add Crypto Testability Audit Report

[Maatify]

Added TESTABILITY_AUDIT.md containing a comprehensive review of the maatify/crypto library testability per the requested scope. Includes component analysis for PasswordHasher, HKDFService, ReversibleCryptoService, ReversibleCryptoAlgorithmRegistry, KeyRotationService, CryptoProvider, CryptoContextFactory, and CryptoDirectFactory along with test coverage map, estimated tests, and refactoring analysis.

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PR created automatically by Jules for task 11830616385575121883 started by @Maatify

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