Fix WireGuard decryption failures

- Fix BLAKE2s final block handling when len == fill
- Fix key derivation order based on is_initiator flag
- Add missing header files (se050_i2c_hal.h, se050_scp03.h)
- Fix missing type definitions and includes
- Update tests to set is_initiator and matching keys

All 24 tests now pass.

include/se050_keystore_internal.h

@@ -11,6 +11,7 @@
 #define SE050_KEYSTORE_INTERNAL_H
 
 #include "se050_wireguard.h"
+#include "se050_session_internal.h"
 #include <stdint.h>
 #include <stddef.h>
 
@@ -51,6 +52,8 @@ typedef struct {
 /**
  * @brief Key store context structure
  */
+typedef struct se050_keystore_ctx se050_keystore_ctx_t;
+
 struct se050_keystore_ctx {
     se050_session_ctx_t *session;       /**< Associated session */
     key_object_t *objects;              /**< Key objects array */