fix: resolve additional mypy errors (jwt, langchain)

- Add jwt to mypy ignore list for mcp_proxy_guard.py
- Add disallow_untyped_calls=false override for langchain integration
- Fix method-assign type: ignore comment in langchain.py

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

Author: sattyamj-attri

pyproject.toml

@@ -159,9 +159,15 @@ module = [
     "opentelemetry.*",
     "langchain_core",
     "langchain_core.*",
+    "jwt",
+    "jwt.*",
 ]
 ignore_missing_imports = true
 
+[[tool.mypy.overrides]]
+module = "agent_airlock.integrations.langchain"
+disallow_untyped_calls = false
+
 [tool.pytest.ini_options]
 testpaths = ["tests"]
 asyncio_mode = "auto"