[CHORE]: graphviz_server — migrate from standalone fastmcp to mcp>=2,<3 MCPServer

[jonpspri]

Summary

After the server has been moved to this repository (tracked in #27), update mcp-servers/python/graphviz_server/ to migrate from the standalone fastmcp package to the MCP SDK v2 MCPServer.

Changes required

1. Dependency swap

# Before
fastmcp>=3.4.4

# After
mcp>=2,<3

2. FastMCP → MCPServer rename

The standalone fastmcp package (jlowin/fastmcp) is a separate project from mcp.server.fastmcp. Confirm the import in server_fastmcp.py and update accordingly:

# Before (standalone fastmcp package)
from fastmcp import FastMCP
app = FastMCP('graphviz-server')

# After (MCP SDK v2)
from mcp.server import MCPServer
app = MCPServer('graphviz-server')

Note: If the server uses standalone fastmcp-specific APIs with no equivalent in mcp.server.MCPServer, document the gap and decide whether to keep fastmcp as an explicit dependency instead.

3. Rename entry-point module (optional)

Consider renaming server_fastmcp.py → server.py now that the FastMCP dependency is removed, and updating pyproject.toml [project.scripts] accordingly.

Acceptance criteria

• fastmcp dependency replaced with mcp>=2,<3
• No remaining fastmcp imports
• All tests pass against MCP SDK v2
• CI green

References

• Depends on: [CHORE]: Move mcp_eval_server to mcp-servers/python/mcp_eval_server #27 (move issue)
• MCP SDK v2 migration epic: CF 1.x (x>0) - Support for MCP 2026-07-28 dual-era communication in ContextForge Gateway mcp-context-forge#6218
• Step 10 (mcp-servers update): [CHORE]: MCP SDK v2 — Update mcp-servers subpackages: FastMCP rename, dependency pins (Step 10/11) mcp-context-forge#6228