Add server.json for MCP Registry publishing

[DaleSeo]

In preparation for publishing Apollo MCP Server to the official MCP Registry at registry.modelcontextprotocol.io, this PR adds server.json configuration file and adds the io.modelcontextprotocol.server.name label Dockerfile for registry verification.

I haven't updated our release process to automatically publish our server to the MCP registry yet. I suggest that we do it manually for the next release and then consider how we can integrate it into our process for future releases.

Testing

Failed to publish the latest release v1.3.0, which was expected because the Docker image wasn't built with the required label.

$ mcp-publisher publish
Publishing to https://registry.modelcontextprotocol.io...
Error: publish failed: server returned status 400: {"title":"Bad Request","status":400,"detail":"Failed to publish server","errors":[{"message":"registry validation failed for package 0 (ghcr.io/apollographql/apollo-mcp-server:v1.3.0): OCI image 'ghcr.io/apollographql/apollo-mcp-server:v1.3.0' is missing required annotation. Add this to your Dockerfile: LABEL io.modelcontextprotocol.server.name=\"io.github.apollographql/apollo-mcp-server\""}]}

So, I built a canary release from this PR: https://github.com/apollographql/apollo-mcp-server/pkgs/container/apollo-mcp-server/639103678?tag=canary-20260112T145439Z-114c866

And then, published it to the registry and it was successful 🎉: https://registry.modelcontextprotocol.io/?q=apollo-mcp-server

$ mcp-publisher publish
Publishing to https://registry.modelcontextprotocol.io...
✓ Successfully published
✓ Server io.github.apollographql/apollo-mcp-server version canary-20260112T145439Z-114c866

[apollo-librarian]

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Build ID: e35836fb7f89b6a7bd4717f3
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[gocamille]

🎉