MCP endpoint for AI agents (Streamable HTTP)

Model Context Protocol endpoint — Streamable HTTP transport, JSON-RPC 2.0 over POST. Exposes the same capabilities as this REST API as 5 MCP tools: validate_iban, batch_validate_iban, lookup_bic, check_compliance, lookup_ch_clearing. Flow: POST an initialize request, then tools/list and tools/call (include the returned Mcp-Session-Id header on follow-up calls). Also available as a stdio server via npx -y ibanforge-mcp. This path speaks MCP, not the REST conventions documented elsewhere in this spec.