chore: remove unused jan_utils::string::parse_uuid (hardware plugin has its own copy)

[bitcompass]

Problem Statement

Two parse_uuid implementations exist with the same signature:

• src-tauri/utils/src/string.rs:2 — pub fn parse_uuid(bytes: &[u8; 16]) -> String in jan_utils.
• src-tauri/plugins/tauri-plugin-hardware/src/vendor/vulkan.rs:21 — private fn parse_uuid(bytes: &[u8; 16]) -> String local to the hardware plugin.

The hardware plugin does not depend on jan_utils, so it cannot use the shared version. The shared version has zero external callers — only its own tests. Effectively, the jan_utils copy is dead code.

Feature Idea

Pick one of two equally small options (either is fine; I recommend option A unless there is an existing plan to pull jan_utils into tauri-plugin-hardware):

Option A — delete the dead helper:

1. Delete parse_uuid and the three #[test] cases (test_parse_uuid*) from src-tauri/utils/src/string.rs.
2. Run cargo check / cargo test -p jan_utils.

Option B — use the shared helper:

1. Add jan-utils = { path = "../../../utils" } to tauri-plugin-hardware/Cargo.toml.
2. Replace the local parse_uuid in vulkan.rs with use jan_utils::string::parse_uuid;.
3. Delete the plugin's local copy.