fix: update mcp version in requirements.txt to >=1.25

requirements.txt had mcp==1.18.0 but pyproject.toml requires
mcp>=1.25,<2. The old version caused ImportError in server.py's
try block, preventing list_tools/call_tool from being defined,
breaking all test_mcp_server.py tests in CI.

Also loosened pins on mcp's transitive deps (sse-starlette,
starlette, uvicorn, python-multipart) to allow mcp 1.25+ to
install its required versions.

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

requirements.txt

@@ -15,7 +15,7 @@ idna==3.11
 iniconfig==2.3.0
 jsonschema==4.25.1
 jsonschema-specifications==2025.9.1
-mcp==1.18.0
+mcp>=1.25,<2
 packaging==25.0
 pluggy==1.6.0
 pydantic==2.12.3
@@ -30,15 +30,15 @@ pytest==8.4.2
 pytest-asyncio==0.24.0
 pytest-cov==7.0.0
 python-dotenv==1.1.1
-python-multipart==0.0.20
+python-multipart>=0.0.20
 referencing==0.37.0
 requests==2.32.5
 rpds-py==0.27.1
 sniffio==1.3.1
 soupsieve==2.8
-sse-starlette==3.0.2
-starlette==0.48.0
+sse-starlette>=3.0.2
+starlette>=0.48.0
 typing-inspection==0.4.2
 typing_extensions==4.15.0
 urllib3==2.5.0
-uvicorn==0.38.0
+uvicorn>=0.38.0