fix: enforce miniapp two-step secret flow for signing

[Gaubee]

Closes #499

Summary

• enforce two-step secret flow in miniapp sign sheet: when account requires second secret, pattern step now routes to two-step input before signing
• enforce the same rule in miniapp transfer confirm sheet to keep behavior consistent with Send flow
• expand two-step secret error recognition to include signSignature is required / 001-11003
• add regression tests for two-step gating and error detection
• bump version to 1.0.20 and update changelog

Validation

• pnpm vitest run src/stackflow/activities/sheets/__tests__/miniapp-auth.test.ts src/stackflow/activities/sheets/MiniappConfirmJobs.regression.test.tsx
  • 26 passed