feat: Add SE050 hardware RNG integration

- Added system RNG fallback using /dev/urandom
- Created se050_wireguard_se050_rng.c for SE050 TRNG integration
- WireGuard can now use SE050's built-in hardware random number generator
- Improved test coverage: 28 passing tests

Usage for SE050 RNG:

For standalone (no SE050):

include/se050_wireguard.h

@@ -170,12 +170,32 @@ int se050_wireguard_compute_mac2(se050_wireguard_session_t *session,
 /**
  * @brief Generate a new WireGuard keypair
  * 
+ * Uses system RNG (/dev/urandom on POSIX).
+ * For SE050 hardware RNG, use se050_wireguard_generate_keypair_se050().
+ * 
  * @param private_key Output: private key (32 bytes)
  * @param public_key Output: public key (32 bytes)
  * @return 0 on success, -1 on error
  */
 int se050_wireguard_generate_keypair(uint8_t *private_key, uint8_t *public_key);
 
+/**
+ * @brief Generate WireGuard keypair using SE050 hardware RNG
+ * 
+ * This function uses the SE050 chip's built-in True Random Number Generator
+ * for cryptographically secure key generation.
+ * 
+ * @param session SE050 session context (initialized via se050_session_init())
+ * @param private_key Output: private key (32 bytes)
+ * @param public_key Output: public key (32 bytes)
+ * @return 0 on success, -1 on error
+ */
+#ifdef SE050_ENABLED
+int se050_wireguard_generate_keypair_se050(se050_session_ctx_t *session,
+                                           uint8_t *private_key, 
+                                           uint8_t *public_key);
+#endif
+
 /* =========================================================================
  * Constants
  * ========================================================================= */