feat: add mcp server foundation and CLI integration

[dolliecoder]

What type of PR is this?

/kind feature

What this PR does / why we need it:
This PR lays the architectural foundation for the Kmesh Model Context Protocol (MCP) Server
Specifically, this PR:

1. Adds the github.com/mark3labs/mcp-go SDK dependency to go.mod.
2. Creates the core KmeshMCPServer struct in mcp/server/server.go to handle MCP initialization.
3. Wires up the new kmeshctl mcp serve subcommand for local AI agents.
4. Creates a standalone entrypoint in mcp/cmd/mcp-server/main.go for future containerization.

This establishes the baseline infrastructure so that subsequent PRs can focus entirely on migrating the core dump, log, authz, and secret capabilities into callable MCP tools.

Which issue(s) this PR fixes:
Fixes #1916

Special notes for your reviewer:
This is a foundational PR to establish the CLI skeleton and dependencies, so no core Kmesh data is being exposed yet. The mcp-go SDK was chosen because it provides robust, native support for both STDIO (used by Cursor/Claude Desktop) and SSE transport.

Does this PR introduce a user-facing change?:

Added the `kmeshctl mcp serve` command to run the Kmesh Model Context Protocol server.

[kmesh-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[kmesh-bot]

Adding label do-not-merge/contains-merge-commits because PR contains merge commits, which are not allowed in this repository.
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