device-voice-h5/openspec/changes/add-iccid-login-check-digit-retry/tasks.md

1. Login fallback

• 1.1 Add a pure ISO/IEC 7812 Luhn mod-10 check-digit helper for a 19-digit ICCID prefix.
• 1.2 Retry asset verification once and silently only when the initial identifier matches ^89\\d{17}$ and the first verification fails or lacks asset_token.
• 1.3 Persist the completed ICCID only after the retry succeeds; retain the existing visible error path for all final failures and non-matching identifiers.

2. Verification

• 2.1 Verify known Luhn vectors plus first-attempt success, fallback success, fallback failure, and non-ICCID failure behavior.
• 2.2 Run the H5 production build.