Other references: Charles Ambrose referred to Colt as a 'golf architect' in 1911 when advising Walter Tarrant to abandon his initial idea to get house buyers to lay out individual holes at St George's Hill. Darwin used the phrase extensively in
The Golf Courses of the British Isles (1910); it seems to have been in fairly common usage by then.
However, this is the earliest reference I've been able to find in the UK press. It comes from the
Dundee Evening Telegraph of Tuesday 16 August 1904. I find it pretty unlikely that the paper's anonymous golf writer invented the term; logically therefore I surmise it must have been in relatively common use then.