Temperature of the beer affects how much CO2 will remain in solution after fermentation is complete and CO2 is no longer being produced. Use the fermentation temperature if bottling immediately after fermentation is complete.
Use the temperature your beer rests/ages at after fermentation is complete if this period of time is more than a few days. During this time period CO2 in solution will be released. More CO2 will be released if the rest temperature is 72° than will be released at a temperature of 60°.
Cold crashing will temporarily halt the release of the CO2 that was in solution before the crash, but CO2 will not be increased since fermentation and CO2 production has ended.
For carbonation calculations use the rest temperature before the cold crash if the beer will not be warmed for a few days before bottling. If the beer is allowed to warm for a few days, after the cold crash, use the current temperature at bottling time.