The ornamental design for a built-in household coffee machine, as shown and described.
1. Built-in household coffee machine
1.1 : Perspective
1.2 : Perspective view 2
1.3 : Perspective view 3
1.4 : Perspective view 4
1.5 : Front
1.6 : Reference view
The evenly-spaced broken lines depict portions of the built-in household coffee machine that form no part of the claimed design; the dash-dot-dash broken lines define the boundary of the claimed design and form no part thereof; the dash-dot-dot-dash broken line in reproduction 1.6 is included to show a partially enlarged view only and forms no part of the claimed design; reproduction 1.1 is a top left perspective view of the built-in household coffee machine; reproduction 1.2 is a top right perspective view thereof; reproduction 1.3 is a bottom left perspective view thereof; reproduction 1.4 is a bottom right perspective view thereof; reproduction 1.5 is a front view thereof; and reproduction 1.6 is a reference view in which the claimed design is installed on an unclaimed wall; this design is for a built-in household coffee machine made of glass, synthetic resin and metal.