docs(aes,des): add crate documentation and improve re-exports

Add crate-level doc comments with usage examples. Export additional
types for library users:
    - aes: Block32 (32-bit word type)
    - des: LR (Feistel round state)

aes/src/lib.rs

@@ -1,3 +1,16 @@
+//! AES (Advanced Encryption Standard) implementation.
+//!
+//! Provides AES-128 block cipher with 128-bit keys and blocks.
+//!
+//! # Example
+//! ```
+//! use aes::Aes;
+//! use cipher_core::BlockCipher;
+//!
+//! let cipher = Aes::new(0x2b7e1516_28aed2a6_abf71588_09cf4f3c_u128);
+//! let ciphertext = cipher.encrypt(&[0u8; 16]).unwrap();
+//! ```
+
 mod aes;
 mod block;
 mod constants;
@@ -5,4 +18,4 @@ mod key;
 mod operations;
 mod sbox;
 
-pub use {aes::Aes, block::Block128};
+pub use {aes::Aes, block::Block128, block::Block32};

des/src/lib.rs

@@ -1,7 +1,21 @@
+//! DES (Data Encryption Standard) implementation.
+//!
+//! Provides the classic DES block cipher with 64-bit keys and blocks.
+//! Uses 16 Feistel rounds with 48-bit subkeys.
+//!
+//! # Example
+//! ```
+//! use des::Des;
+//! use cipher_core::BlockCipher;
+//!
+//! let cipher = Des::new(0x133457799BBCDFF1_u64);
+//! let ciphertext = cipher.encrypt(&[0u8; 8]).unwrap();
+//! ```
+
 mod block;
 pub mod constants;
 mod des;
 mod key;
 pub mod utils;
 
-pub use {block::Block64, des::Des};
+pub use {block::Block64, block::LR, des::Des};