fix(sdk-core,express): allow passwordless OFC wallet generation

[zahin-mohammad]

Description

Allow OFC trading wallets created with userKeySigningRequired: false to omit passphrase and passcodeEncryptionCode.

The exported Go Account options codec now models both valid request shapes:

• password-backed generation requires both password fields and accepts userKeySigningRequired omitted, true, or false;
• passwordless generation requires userKeySigningRequired: false and omits both password fields.

Supplying only one password field is rejected. The passwordless path uploads a public-only structural user keychain and omits encryptedWalletPassphrase; the existing password-backed encryption behavior is unchanged.

Issue Number

WCN-1859

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• yarn --cwd modules/express mocha --no-config --require tsx --timeout 60000 test/unit/typedRoutes/generateWallet.ts — 22 passing
• yarn --cwd modules/sdk-core nyc -- mocha test/unit/bitgo/wallet/walletOptionsCodecs.ts test/unit/bitgo/wallet/walletsGoAccount.ts — 14 passing
• yarn --cwd modules/sdk-core build --force
• yarn --cwd modules/express build
• Complete Express suite: 1,915 passing with one transient socket hang up in the canonical-address suite; isolated rerun of that suite passed 60/60.

Tested with the repository-pinned Node.js 24.13.0.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My code compiles correctly
• My commits follow Conventional Commits
• The ticket was included in the commit message
• I have added tests that prove the fix is effective
• Relevant existing and new unit tests pass locally

[linear-code]

WCN-1859