[server] Add Authorization Bearer support for MCP clients

[demarant]

Contribution Type

• Recipe (/recipes)
• Schema (/schemas)
• Dashboard (/dashboards)
• Integration (/integrations)
• Skill (/skills)
• Repo improvement (docs, CI, templates)

What does this do?

Adds standard HTTP Authorization: Bearer authentication support to the Open Brain MCP server. Enables Perplexity Pro and other MCP clients that only support standard auth headers to connect directly without needing a proxy. Maintains backward compatibility with the existing x-brain-key header and ?key= query parameter.

Fixes

• [feature] Perplexity Pro MCP compatibility #73

Testing

• Tested on Perplexity web and mobile app
• Successfully retrieved and stored thoughts via MCP tools

Requirements

• Working Open Brain setup with deployed MCP server
• Perplexity Pro or other MCP client requiring standard Bearer auth
• No additional external services or tools required

Checklist

• I've read CONTRIBUTING.md
• This is a core server change, not a new contribution with README — no additional documentation required
• My metadata.json has all required fields — N/A (server code change, not a contribution folder)
• If my contribution depends on a skill or primitive, I declared it in metadata.json and linked it in the README — N/A
• I tested this on my own Open Brain instance — Tested on Perplexity web and mobile app
• No credentials, API keys, or secrets are included

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Note: This is a core infrastructure change (server code), not a new recipe/integration. The PR includes:

• server/index.ts — Core MCP server with Bearer auth
• integrations/kubernetes-deployment/index.ts — Self-hosted variant
• extensions/_template/AGENT_SPEC.md — Updated canonical template