fix(deps): remove unused chrono dependency from src-tauri

The chrono dependency is used in snowflake-core, not src-tauri directly.
Fixes cargo-machete CI check.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: fazxes

Cargo.lock

@@ -40,7 +40,6 @@ futures = { workspace = true }
 thiserror = { workspace = true }
 crossbeam-channel = { workspace = true }
 hashbrown = { workspace = true }
-chrono = { workspace = true }
 
 # Tauri
 tauri = { workspace = true, features = ["tray-icon"] }