## 1. Login fallback

- [x] 1.1 Add a pure ISO/IEC 7812 Luhn mod-10 check-digit helper for a 19-digit ICCID prefix.
- [x] 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`.
- [x] 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

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