#1027 /api/v1/mcp/servers routes carry no permission check

Found during #1001: GET/POST /api/v1/mcp/servers and DELETE /api/v1/mcp/servers/<name> (api/mcp_registry.py) check only g.tenant_id. Any member of a tenant, including a viewer, can register a server (and its bearer token) or remove one. EARS: If the caller lacks the manage permission for integrations/secrets in the tenant, then the MCP server routes shall return 403 before any DB work.