docs: add OAuth and popular MCP client setup

[9trocode]

Summary

• document OAuth and Bearer-token setup for ChatGPT, Claude, Cursor, Codex, VS Code and GitHub Copilot, Gemini CLI, Windsurf, and Zed
• add a compatibility matrix, least-privilege guidance, security recommendations, and OAuth troubleshooting
• explain the one-time PipeOps-hosted service-token exchange without implying controller or Console changes
• fix the production docs image so HOST and PORT survive the Docker stage boundary
• add .dockerignore so local build output and dependencies are not sent in the Docker context

Dependency

The OAuth instructions should publish with or after the PipeOps MCP OAuth bridge is deployed from PipeOpsHQ/pipeops-mcp.

Verification

• yarn build
• production Docker image build
• runtime smoke with PORT=3000 and HOST=0.0.0.0
• docs page returned HTTP 200 at /docs/integrations/pipeops-mcp
• container log confirmed Serving build directory at: http://0.0.0.0:3000/

The Docusaurus build still reports one pre-existing broken anchor in /docs/projects/gitops; this PR does not add broken links or anchors.