feat(cli): add helpers module (vault_dir/L8, git_command/H4, iso8601/M11)

Bumps rpassword to 7.x (H7) and adds zeroize/chrono/assert_cmd dev-deps.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/relicario-cli/Cargo.toml

@@ -12,8 +12,9 @@ path = "src/main.rs"
 relicario-core = { path = "../relicario-core" }
 clap = { version = "4", features = ["derive"] }
 anyhow = "1"
-rpassword = "5"
+rpassword = "7"
 arboard = "3"
+chrono = { version = "0.4", default-features = false, features = ["clock"] }
 dirs = "5"
 hex = "0.4"
 ed25519-dalek = { version = "2", features = ["rand_core"] }
@@ -21,3 +22,8 @@ rand = "0.8"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 zeroize = "1"
+
+[dev-dependencies]
+assert_cmd = "2"
+predicates = "3"
+tempfile = "3"