[Fix] Fix union handling in ED25519 key loading to prevent memory corruption

[Fix] Fix union handling in ED25519 key loading to prevent memory corruption

When loading ED25519 keys from PEM, the code was writing to key_eddsa in the
union and then attempting to free key_ssl pointers, which corrupted the
key_eddsa pointer and caused use-after-free/double-free during cleanup.

The fix saves the EVP_PKEY and BIO pointers to temporary variables, extracts
the raw key, frees the OpenSSL objects, and only then assigns to the union.
This prevents memory corruption and resource leaks.