fix: stabilize miniapp transfer fifo flow and timeout fallback

[Gaubee]

Summary

• unify miniapp transfer sheet multi-step state and i18n copy
• return transaction objects consistently for bio_sendTransaction
• harden FIFO release by tying queue release to sheet closed event
• add unmount settle fallback (emit cancel + sheet closed) to avoid hanging bio_sendTransaction
• clone signed transaction payload to avoid cross-request mutation leaks
• add regression tests for requestId routing, unmount fallback, and consecutive transfers

Validation

• pnpm typecheck
• pnpm test
• pnpm vitest run src/stackflow/activities/sheets/MiniappConfirmJobs.regression.test.tsx src/stackflow/activities/sheets/__tests__/miniapp-transfer-error.test.ts src/stackflow/activities/sheets/__tests__/miniapp-step-flow.test.ts src/stackflow/activities/sheets/__tests__/miniapp-auth.test.ts src/services/ecosystem/__tests__/transfer-handler.test.ts src/services/ecosystem/__tests__/sheet-queue.test.ts