MCP: connect several organizations from one client

The Pierrr MCP server now accepts several personal access tokens in a single Authorization header, comma-separated (one per organization), so one AI client config can drive every organization you belong to.
Every tool call for a multi-org token must say which organization it targets, via an organizationId or organizationSlug argument. The MCP catalog advertises this requirement on each tool once your token covers more than one organization.
Single-token setups are unaffected: no selector needed, behavior is unchanged.
A missing or invalid selector on a multi-org token returns a clear error listing the organizations available on that token, instead of a silent failure.