feat(cli): hint users for newer version

[goulvenclech]

Sampo now checks for updates once per day, and displays a hint when a newer version is available on crates.io. The check is non-blocking and fails silently if offline.

What does this change?

• crates/sampo/src/version_check.rs (new): Queries crates.io for the latest version, caches results for 24h using platform-appropriate directories via dirs, and compares versions using semver.

• crates/sampo/src/ui.rs: Adds log_hint() function for displaying non-critical suggestions with a 💡 prefix in yellow.

• crates/sampo/src/main.rs: Calls version check at startup and prints a hint if an update is available.

• crates/sampo/Cargo.toml: Adds dirs dependency for cross-platform cache directory resolution.

How is it tested?

• crates/sampo/src/version_check.rs: Unit tests cover cache entry serialization/parsing, semver comparison logic, and edge cases (invalid versions, pre-releases).

How is it documented?

N/A.

[sampo-s-bot]

🧭 Changeset detected

Merging this PR will release the following updates:

sampo (Cargo) — minor version bump

Minor changes

• Sampo now checks for updates once per day, and displays a hint when a newer version is available on crates.io. The check is non-blocking and fails silently if offline.