fix: Python 3.9 compat — add __future__ annotations for str | Path union

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: QuantQJ

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "modelsign"
-version = "1.0.2"
+version = "1.0.3"
 description = "Sign AI models with identity. Verify anywhere."
 authors = [{name = "QJ", email = "qj@constantone.ai"}]
 license = {text = "Apache-2.0"}

src/modelsign/__init__.py

@@ -1,6 +1,6 @@
 """modelsign — Sign AI models with identity. Verify anywhere."""
 
-__version__ = "1.0.2"
+__version__ = "1.0.3"
 
 from modelsign.identity.card import ModelCard, validate_card
 from modelsign.identity.canonical import canonical_json

src/modelsign/middleware/response.py

@@ -1,5 +1,7 @@
 """Ed25519 response signing for API authenticity."""
 
+from __future__ import annotations
+
 import base64
 import hashlib
 from datetime import datetime, timezone