fix: support cryptography < 3.0 API for X25519 key serialization

private_bytes_raw() was added later; fall back to private_bytes(Raw)
for older system packages (e.g. Debian Bookworm python3-cryptography).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/setup_cell.py

@@ -100,9 +100,15 @@ def _gen_keys_python():
     """Generate WireGuard keypair using the cryptography library (no wg binary needed)."""
     import base64
     from cryptography.hazmat.primitives.asymmetric.x25519 import X25519PrivateKey
+    from cryptography.hazmat.primitives.serialization import Encoding, PublicFormat, PrivateFormat, NoEncryption
     private_key = X25519PrivateKey.generate()
-    private_bytes = private_key.private_bytes_raw()
-    public_bytes = private_key.public_key().public_bytes_raw()
+    try:
+        # private_bytes_raw() available in cryptography >= 3.0
+        private_bytes = private_key.private_bytes_raw()
+        public_bytes = private_key.public_key().public_bytes_raw()
+    except AttributeError:
+        private_bytes = private_key.private_bytes(Encoding.Raw, PrivateFormat.Raw, NoEncryption())
+        public_bytes = private_key.public_key().public_bytes(Encoding.Raw, PublicFormat.Raw)
     return base64.b64encode(private_bytes).decode(), base64.b64encode(public_bytes).decode()