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

src/lib.rs

@@ -0,0 +1,6 @@
+pub mod archive;
+pub mod cli;
+pub mod compression;
+pub mod crypto;
+pub mod format;
+pub mod key;