Update SCP03 tests with PlatformSCP03 integration tests and documentation

- Add PlatformSCP03 integration test cases (test_scp03_platform_integration, test_scp03_platform_key_file)
- Update test helpers with mock session creation
- Update README with PlatformSCP03 configuration guide
- Add references to NXP AN12413 and AN12436
- Fix test assertions to work with opaque session type

include/se050_session_internal.h

@@ -0,0 +1,37 @@
+/**
+ * @file se050_session_internal.h
+ * @brief SE050 Session Internal Definitions
+ * 
+ * Internal definitions for session implementation.
+ * 
+ * License: MIT (Clean-room implementation)
+ */
+
+#ifndef SE050_SESSION_INTERNAL_H
+#define SE050_SESSION_INTERNAL_H
+
+#include "se050_wireguard.h"
+#include <stdint.h>
+
+/* Session states */
+typedef enum {
+    SESSION_STATE_CREATED = 0,
+    SESSION_STATE_OPENED,
+    SESSION_STATE_CLOSED,
+} session_state_t;
+
+/**
+ * @brief Session context structure
+ */
+struct se050_session_ctx {
+    se050_i2c_hal_t *hal;           /**< I2C HAL interface */
+    session_state_t state;          /**< Current session state */
+    uint32_t session_id;            /**< Unique session identifier */
+    uint8_t session_key[32];        /**< Session encryption key */
+    size_t session_key_len;         /**< Session key length */
+    uint32_t cmd_counter;           /**< Command counter for SCP03 */
+    uint32_t resp_counter;          /**< Response counter for SCP03 */
+    se050_rng_ctx_t *rng;           /**< RNG context */
+};
+
+#endif /* SE050_SESSION_INTERNAL_H */