Hyundai Elantra CN7 (EU) not automatically fingerprinted — requires manual CN7 2021 override

### Describe the car bug

Car: Hyundai Elantra CN7 (2021), European-market build, with Smart Cruise Control (SCC).

Automatic car fingerprinting does not recognize this car at all on stock openpilot, so it cannot engage/drive normally. The only way to get it running is via sunnypilot, manually overriding the platform selection to HYUNDAI_ELANTRA_2021 (CN7). With that manual override, longitudinal and lateral control work correctly, including the OEM Smart Cruise Control interface.

This points to a firmware/ECU mismatch in the FW_VERSIONS fingerprint table for this platform rather than a real behavioral difference. EU-market CN7 units apparently ship ECU firmware versions that are not present in opendbc's fingerprint entries for HYUNDAI_ELANTRA_2021, so FW-based fingerprinting (Fingerprinting 2.0) never matches and the car falls back to unsupported instead of auto-selecting CN7 2021.

Attached is a public route from a normal drive with the manual CN7 2021 override active, for reference on this car's CAN/FW behavior.

Steps to reproduce:
1. Install comma 4 / panda on a EU-spec Hyundai Elantra CN7 (2021, SCC-equipped).
2. Power on and start the car with stock openpilot (no manual fingerprint override).
3. Car is not recognized — fingerprinting fails to match HYUNDAI_ELANTRA_2021, so openpilot cannot engage properly.
4. Manually forcing the CN7 2021 (HYUNDAI_ELANTRA_2021) platform in sunnypilot works correctly — confirming it is the right platform, just not reachable via automatic FW fingerprinting for this EU firmware revision.

### Provide a route where the issue occurs

https://connect.comma.ai/4db9a4d26f328177/00000026--c5876b04d9

### openpilot version

sunnypilot (fork) — exact release TBD, will confirm; base opendbc fingerprint tables are shared with stock openpilot so this is not fork-specific behavior

### Additional info

Willing to help pull ECU firmware versions via UDS from this route (or a fresh one) to add proper entries to FW_VERSIONS in opendbc/car/hyundai/fingerprints.py, following the Fingerprinting guide. Happy to coordinate on Discord if that is a better place to work through it.

i told claude to do all this so idk what it did

Start with the linked route and the Fingerprinting guide, then inspect opendbc/car/hyundai/fingerprints.py for the HYUNDAI_ELANTRA_2021 FW_VERSIONS entries. Collect the EU CN7 ECU firmware versions through UDS and compare them with the existing entries. Done means automatic fingerprinting selects HYUNDAI_ELANTRA_2021 without a manual override.

Written by the indexing model from the issue text.