fix(worldremit): validate payout inputs

[aiirvizionz]

Summary

• Validate WorldRemit payout recipient, amount, and currency before returning a transfer id.
• Reject blank recipients, non-positive/non-finite amounts, and malformed currency codes early.
• Add regression coverage so invalid payout requests cannot look like successful transfers.

Validation

• git diff --check
• node node_modules\vitest\vitest.mjs run packages/payments/worldremit/src/index.test.ts (5 tests passed)

This checkout's standard pnpm flow is currently blocked during dependency preparation by the committed lockfile policy issue around @profullstack/autoblog@0.4.0 lacking a tarball integrity field, so I used the already-present Vitest runtime directly and did not modify the lockfile.

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