Description

Adds Permit2 SignatureTransfer fee authorization as an alternative to Safe execTransaction for fee collection. Feature-flagged OFF by default via permit2Enabled and executors fields on the fee collection remote config.

How it works:
When permit2Enabled is true, executors are configured, AND the user's Safe has approved USDC to the Permit2 contract:

1. A Permit2 PermitTransferFrom signature is created (EIP-1271 wrapped for Safe)
2. A random executor is selected from the configured list
3. Both are sent to the relayer alongside the CLOB order

Fallback behavior: If any condition is not met (flag off, no executors, no Permit2 allowance), the existing Safe transaction fee authorization is used. Zero behavior change for existing users.

Conditional approval: The Permit2 USDC approval is only bundled into deposit transactions when permit2Enabled is true — existing users without the flag don't get an extra approval transaction.

Key additions:

• Permit2FeeAuthorization type with safe-permit2 discriminator
• getPermit2Nonce() — bitmap-based nonce reading from Permit2 contract
• createPermit2FeeAuthorization() — EIP-1271 wrapped Permit2 SignatureTransfer signature
• hasPermit2Allowance() — checks Safe USDC approval to Permit2
• extraUsdcSpenders parameter on createAllowancesSafeTransaction, hasAllowances, getProxyWalletAllowancesTransaction for conditional approval
• calculateFees passes through executors and permit2Enabled
• submitClobOrder accepts Permit2 auth union type and executor param
• placeOrder branching: Permit2 → Safe tx fallback
• getAccountState and prepareDeposit conditionally include Permit2 approval

Still uses FOK orders — FAK support comes in the next PR.

Depends on: #26703 (feature flag refactor)

Changelog

CHANGELOG entry: null

Related issues

Fixes: https://consensyssoftware.atlassian.net/browse/PRED-715

Manual testing steps

Feature: Permit2 fee authorization (feature-flagged OFF)

  Scenario: user places orders with Permit2 disabled (default)
    Given user has Predict feature enabled
    And permit2Enabled remote flag is false (default)

    When user places a buy order
    Then fee authorization uses Safe transaction (existing behavior)
    And order type is FOK

  Scenario: user places orders with Permit2 enabled
    Given user has Predict feature enabled
    And permit2Enabled remote flag is true with executors configured
    And user's Safe has approved USDC to Permit2 contract

    When user places a buy order
    Then fee authorization uses Permit2 SignatureTransfer
    And a random executor is selected and sent with the order
    And order type is still FOK

  Scenario: user places orders with Permit2 enabled but no allowance
    Given user has Predict feature enabled
    And permit2Enabled remote flag is true
    And user's Safe has NOT approved USDC to Permit2 contract

    When user places a buy order
    Then fee authorization falls back to Safe transaction

Screenshots/Recordings

N/A — backend logic, no UI changes.

Before

N/A

After

N/A

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• I've followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
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• I've included tests if applicable
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Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
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