While the other answers RAW vs RAI, and I generally agree -- RAW, there is nothing in the spell description that says it HAS to be mechanical/physical in nature so it should work, but RAI it's probably not what the spell was designed to do -- There are other aspects to consider.
First, and foremost, is an unsigned contract, a "trap"?
The characters have a piece of parchment in front of them, filled with words. Is that a trap? Or is it just a thing to sign?
It might be that a contract is merely the POTENTIAL of being a trap. The "trap" doesn't exist until signed. But I digress...
For contracts, "trap" is very subjective
To that point, what some people would call a "trap" might actually just be boilerplate text. An example we've probably all run across is forced arbitration. It generally stacks the deck in favor of the contract writer, but wouldn't be a "trap". It clearly says that in case of dispute, it will not be settled by judge and jury, but by an "impartial" arbitrator. Trap? No, but maybe not what you want when there is a dispute.
Or for a more classical/fictional example; was the contract used by Willy Wonka a "trap"?
I, the undersigned, shall forfeit all rights, privileges, and licenses herein and herein contained, et cetera, et cetera... Fax mentis incendium gloria cultum, et cetera, et cetera... Memo bis punitor delicatum!
The contract, presumably, made it extremely easy for the undersigned to do something that would make them lose everything. Was that a "trap" or was it careful wording to ensure that the contract was always broken so that the winner was always chosen on the whim of Willy Wonka?
Is it a trap only if the the parties are bound in some way beyond their expectation, or is it a trap if it is easily broken as to free the parties to do as they will?
What if the contract is legitimately for a trap? The contract states that the party will build a trap, or be part of a trap; what happens?
The spell itself is a trap
This spell merely reveals that a trap is present. You don't learn the location of each trap, but you do learn the general nature of the danger posed by a trap you sense.
What is the "nature" of a contractual trap? Could it be explained away by anything else in the room? The chest in the corner could be a trap. The thief that walked by the window could be a danger. The devil offering you a contract is a threat with or without a contract.
Everything is up to the DM
It is unlikely that any actual contract, or other legal document, is being drafted. So the contents of which are entirely on what the DM thinks it should contain.
Likewise, the effectiveness of the spell is up to the DM as well.
If kobolds used rotten planks to cross a chasm, is it a trap? What if they could only find rotten planks so they used what was available? They are light enough to cross without breaking the boards so they don't care. The DM has final say.
What if every contract includes the "Find Trap" clause?
This contract, and all items pertaining to the undersigned "soul", is null and void for the duration, and only for the duration, in which the contract is subject to the "Find Trap" spell or other similar magical and non-magical effects, or in the range of said effects. This includes if the effect is handled though an intermediary such as familiar, dominated creatures, scrying, clairvoyance, and other means not listed above.
So while examining the contract, the trap is not valid so therefore not subject to trigger the spell.
The slippery slope
How would this go beyond contracts? If you cast it on the guy offering candy from the back of their windowless van, would it show up as a trap? What about the friendly barkeep that says he overheard about a get-rich-quick scheme? Or the blacksmith that sells you a cursed weapon?
Where does sensing "the presence of a trap" end?
In the end, it may cause more trouble that it's worth
Players will get grumpy when the spell works for some "traps" but not others. For instance, with the kobolds scenario above, since there was no malice in placing the board, it wasn't a "trap". But, last session, when the bandits did the same thing with rotten wood it WAS a trap because they knew it wouldn't support pursuers.
Now multiply that with all the other things that can be screened; shop keeps, mission-giving NPCs, objects, places, etc... I would leave the spell alone unless it really furthers the story.