feat(03-01): create library crate, update main.rs imports, add dev-dependencies

- Create src/lib.rs re-exporting all modules as public
- Update main.rs to use encrypted_archive:: imports instead of local mod declarations
- Add dev-dependencies: tempfile, assert_cmd, hex-literal, predicates

Cargo.toml

@@ -12,3 +12,9 @@ flate2 = "1.1"
 clap = { version = "4.5", features = ["derive"] }
 rand = "0.9"
 anyhow = "1.0"
+
+[dev-dependencies]
+tempfile = "3.16"
+assert_cmd = "2.0"
+hex-literal = "0.4"
+predicates = "3.1"