chore(deps): update rand to 0.10.2

[VerifiedOrganic]

Summary

Update the locked rand release from 0.10.1 to 0.10.2 as an isolated maintenance slice rebuilt from current main. Upstream 0.10.2 includes a UniformChar deserialization soundness fix plus two small safety/documentation changes.

Related: #301

Scope

• change only the rand package version/checksum and its disambiguated references in Cargo.lock
• retain rand_core 0.10.1, getrandom 0.4.2, and the existing resolved feature set
• do not combine AES-GCM, Tokio, rustls, or any other dependency update
• do not modify public APIs or runtime behavior intentionally

The SDK does not enable the rand serde feature and contains no UniformChar, Uniform<char>, or rand-serde use, so this issue does not claim demonstrated exposure to the upstream deserialization defect.

Acceptance criteria

• locked metadata resolves with no unrelated package churn
• all direct rand consumer test suites pass
• serial encrypted-persistence tests pass
• full workspace tests and Clippy with warnings denied pass
• cargo-deny and cargo-audit pass
• final diff is lockfile-only

Upstream evidence

• rand 0.10.2 changelog: https://github.com/rust-random/rand/blob/0.10.2/CHANGELOG.md
• upstream soundness fix: Check UniformChar validity on deser rust-random/rand#1790