ci: Automate version bump to v1.6.0

[illuzen]

Automated version bump for release v1.6.0.

https://github.com/Quantus-Network/quantus-cli/actions/runs/30080077116

Triggered by workflow run: minor

Type:

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Note

Low Risk
Metadata-only version bump; no runtime, security, or behavioral changes.

Overview
Release v1.6.0 — automated minor version bump with no application or library code changes.

Updates the crate version in Cargo.toml and the matching quantus-cli entry in Cargo.lock from 1.5.0 to 1.6.0.

^{Reviewed by Cursor Bugbot for commit 36e6b95. Configure here.}