Add update and check commands with UTC package timestamps

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "depot"
-version = "0.12.2"
+version = "0.13.0"
 edition = "2024"
 
 [lints.rust]
@@ -21,7 +21,7 @@ serde = { version = "1.0.228", features = ["derive"] }
 yaml-rust2 = "0.11.0"
 sha2 = "0.10.9"
 tar = "0.4.44"
-tempfile = "=3.25.0"
+tempfile = "=3.26.0"
 thiserror = "2.0.18"
 toml = "0.9.8"
 url = "2.5.8"
@@ -40,6 +40,7 @@ filetime = "0.2.27"
 clap_complete = "4.5.66"
 clap_mangen = "0.2.31"
 sys-mount = { version = "3.1.0", default-features = false }
+time = { version = "0.3.47", features = ["formatting", "parsing"] }
 
 [dev-dependencies]
-tempfile = "=3.25.0"
+tempfile = "=3.26.0"