Cross-platform: Linux support for Conductor

[mderazon]

This PR adds Linux support to Conductor, including:

• Native system keychain integration via keyring and libsecret.
• Proper sync and verification logic for Linux-specific MCP client paths (VS Code, Antigravity, Claude Desktop).
• Correct handling of environment variable stringification in MCP configurations to prevent parsing errors in clients like Antigravity.
• Enhanced HTTP-to-Stdio proxying with dynamic authentication header detection (e.g., CONTEXT7_API_KEY).
• Absolute path resolution for npx, bunx, and other Node-related commands to ensure reliability in desktop environments where $PATH might be limited.

NOTE: I have tested it on Ubuntu Linux and it was working find. I don't have a Mac to test this on, so I am not sure if it continues working there

[vercel]

@mderazon is attempting to deploy a commit to the aryaarunb's projects Team on Vercel.

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