Unify duplicate sha2 versions in the Rust workspace

### Description of the task

Unify the Rust workspace on a single supported `sha2` version.

The workspace currently contains both `sha2 0.10.x` and `sha2 0.11.x`. PR #791 adds `wxc_common` as another direct consumer of the existing workspace `sha2 = "0.10"` dependency for policy hashing. This does not introduce the original duplication, but it increases the older version's footprint in core binaries.

Expected outcome:

* Inventory the direct and transitive consumers of both versions with `cargo tree`.
* Determine whether the workspace dependency and dependencies retaining `0.10` can move to `0.11`, or otherwise establish a supported single-version plan.
* Update the workspace manifest and lockfile as needed.
* Verify the workspace build, tests, lint, and dependency-feed checks.

### Additional context

Follow-up from the supply-chain review of PR #791.