Fix PyNaCl exception name

Use BadSignatureError instead of BadSignature

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/server.py

@@ -6,7 +6,7 @@ import sys
 from typing import Any
 
 from fastapi import FastAPI, HTTPException, Request, Response
-from nacl.exceptions import BadSignature
+from nacl.exceptions import BadSignatureError
 from nacl.signing import VerifyKey
 
 DISCORD_PUBLIC_KEY = os.environ.get("DISCORD_PUBLIC_KEY", "")
@@ -25,7 +25,7 @@ def verify_signature(
         verify_key = VerifyKey(bytes.fromhex(public_key))
         verify_key.verify(timestamp.encode() + body, bytes.fromhex(signature))
         return True
-    except (BadSignature, ValueError) as e:
+    except (BadSignatureError, ValueError) as e:
         print(f"Signature verification failed: {e}", file=sys.stderr)
         return False