feat: sponsored oft transfers

[melisaguevara]

This PR prepares the swap API to support sponsored flows to HyperCore through our own OFT periphery contracts.

Enabled routes for now:

• USDT → USDT-SPOT
• USDT → USDC-SPOT (waiting on USDC-SPOT address to be available).

It includes:

• Intermediary routing: all transfers route through HyperEVM USDT before reaching HyperCore
• Estimation of maxBpsToSponsor based on real time market simulation for USDT → USDC-SPOT transfers
• Decimal conversion handling between 6-decimal (USDT) and 8-decimal (HyperCore tokens)
• Signature generation fixes to match Solidity contract expectations for on-chain verification
• Transaction building for calling deposit function on SponsoredOFTSrcPeriphery

See this example calls:

• Common params:

{
  "amount": "1000000",
  "inputToken": "0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9",
  "outputToken": "0x200000000000000000000000000000000000010C",
  "originChainId": "42161",
  "destinationChainId": "1337",
  "depositor": "0x9A8f92a830A5cB89a3816e3D267CB7791c16b04D"
}

• exactInput
• exactOutput

See also this Tenderly simulation showing that signature validation is working as expected. Simulation is failing only because of allowance check.

Note: only Arbitrum contract has been deployed as of now.

[linear]

ACX-4609 [API] Craft transaction for sponsored OFT transfers

[vercel]

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Project	Deployment	Preview	Comments	Updated (UTC)
app-frontend-v3	Ready	Preview	Comment	Oct 29, 2025 10:52am
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[melisaguevara]

I moved some functions from oft/strategy to this utils file to reuse them. There should be no changes.

[melisaguevara]

Same here, there should be no changes beyond using the imported utils.

[melisaguevara]

Renamed this strategy to oft-sponsored

[dohaki]

Awesome work! Left some remarks

[dohaki]

LGTM

[dohaki]

I worked on integrating the CCTP sponsored flow on top of your branch but some questions came up.