Hi!
I am sending design of our board with surface mount Photon, this design shows no problems with DHCP/WiFi, but there is only a small batch of <20 boards so far - I cant say it is 100% OK.
You can see the copper pour keepout zone, interrupted side plating…
I use L7805ACD2T voltage regulator dedicated just for Photon with 12V@2A power adapter. The track from voltage regulator to Vin on Photon is 85mm long, 1.27mm wide, 18um copper. There are 100n MLCC and 47uF tantalum caps on the 5V line close to voltage regulator.