feat(sse): add SSE server command

[Fluf22]

What

• extract common code between stdio and sse servers
• add start-sse-server command to CLI
• add config example with gateway to README

Todo

• We could use some more modern server like HonoJS
• OAuth should be done at the server level, not at the MCP app level, to link auth to the user session
• User sessions should be handled by a Redis or similar

[seafoox]

OAuth should be done at the server level, not at the MCP app level, to link auth to the user session

Agree would be great if we could obtain the accessToken connecting to the website, and then setting that one via an ENV variable. In a context like n8n, that would allow to deploy the MCP server one, and declare multiple instance via n8n nodes. Each instance potentially pointing to its own Algolia account.