Add fuzz tests

[Copilot]

Adds fuzz testing infrastructure using cargo-fuzz to discover potential panics or undefined behavior in cryptographic primitives.

Fuzz Targets

• zuc128_keystream / zuc256_keystream - Keystream generation with arbitrary keys/IVs
• zuc128_mac / zuc256_mac - MAC computation including streaming API
• eea3 - Encryption with roundtrip verification
• eia3 - MAC computation including streaming API

CI Integration

Weekly scheduled fuzzing via .github/workflows/fuzz.yml running each target for 60 seconds with matrix parallelization.

Usage

cargo +nightly fuzz run zuc128_keystream -- -max_total_time=60

Original prompt

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This section details on the original issue you should resolve

<issue_title>fuzz tests</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Fuzz Test #28

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