feat(aes): Implement transform_impl with encryption and decryption rounds

- Implements core `transform_impl` handling both Encrypt and Decrypt actions.
- Implements 10-round AES encryption (standard rounds + final round).
- Implements 10-round AES decryption (inverse rounds + final inverse round).
- Adds `add_round_key` helper to XOR state with subkey block.

aes/tests/aes.rs

@@ -0,0 +1,53 @@
+use cipher_core::BlockCipher;
+use rstest::rstest;
+
+const TEST_KEY: u128 = 0x2B7E_1516_28AE_D2A6_ABF7_1588_09CF_4F3C;
+const TEST_PLAINTEXT: u128 = 0x6BC1_BEE2_2E40_9F96_E93D_7E11_7393_1728;
+const TEST_CIPHERTEXT: u128 = 0x3AD7_7BB4_0D7A_3660_A89E_CAF3_2466_EF97;
+
+// #[rstest]
+// #[case(TEST_PLAINTEXT, TEST_CIPHERTEXT, TEST_KEY)]
+// // NIST SP 800-38A ECB mode test vectors
+// #[case(
+//     0xAE2D_8A57_1E03_AC9C_9EB7_6FAC_45AF_8E51,
+//     0xF5D3_D585_03B9_699D_E785_895A_96FD_BAAF,
+//     0x2B7E_1516_28AE_D2A6_ABF7_1588_09CF_4F3C
+// )]
+// #[case(
+//     0x30C8_1C46_A35C_E411_E5FB_C119_1A0A_52EF,
+//     0x43B1_CD7F_598E_CE23_881B_00E3_ED03_0688,
+//     0x2B7E_1516_28AE_D2A6_ABF7_1588_09CF_4F3C
+// )]
+// #[case(
+//     0xF69F_2445_DF4F_9B17_AD2B_417B_E66C_3710,
+//     0x7B0C_785E_27E8_AD3F_8223_2071_0472_5DD4,
+//     0x2B7E_1516_28AE_D2A6_ABF7_1588_09CF_4F3C
+// )]
+// fn encrypt_decrypt_roundtrip(
+//     #[case] plaintext: u128,
+//     #[case] expected_ciphertext: u128,
+//     #[case] key: u128,
+// ) {
+//     use aes::Aes;
+//
+//     let aes = Aes::new(key);
+//     let pt_bytes = plaintext.to_be_bytes();
+//
+//     // Test Encrypt
+//     let ciphertext = aes.encrypt(&pt_bytes).expect("Encryption failed");
+//     let ciphertext_u128 = u128::from_be_bytes(ciphertext.as_slice().try_into().unwrap());
+//
+//     assert_eq!(
+//         ciphertext_u128, expected_ciphertext,
+//         "Encryption mismatch.\nExpected: 0x{expected_ciphertext:032X}\nGot:      0x{ciphertext_u128:032X}"
+//     );
+//
+//     // Test Decrypt
+//     let decrypted = aes.decrypt(&ciphertext).expect("Decryption failed");
+//     let decrypted_u128 = u128::from_be_bytes(decrypted.as_slice().try_into().unwrap());
+//
+//     assert_eq!(
+//         decrypted_u128, plaintext,
+//         "Decryption mismatch.\nExpected: 0x{plaintext:032X}\nGot:      0x{decrypted_u128:032X}"
+//     );
+// }