During Trump's second term, will the Mexican government allocate funds for the construction or maintenance of the US-Mexico border wall, either by spending to help build it or by transferring money to the US expressly for the wall (or border security more generally)?

Money transferred that is not specifically for the border is not sufficient for this to resolve Yes. A statement from the US government is not sufficient for a monetary transfer to be considered "for the wall", if the Mexican government denies it. If the US government (or Trump himself) states that a certain payment is for the wall, and the Mexican government avoids taking any stance on whether that is true, this will resolve according to whether the English-language media describes it as paying for the wall.

The amount of spending does not need to be equivalent to the entire cost of the wall; any amount of "paying for the wall" is enough for this to resolve Yes.

I will not bet on this market.