Store sealed transaction inputs after validation - #2390

This completes Phase 1 by storing the exact sealed transaction inputs accepted by the validator. The validator writes the record only after proof checks, reexecution, and header checks pass. Rejected submissions do not change the database, and a duplicate transaction keeps its first ciphertext.

This record is temporary. Phase 2 will replace it with data encrypted under the validators' threshold key. Anyone with the shared submission secret can decrypt the Phase 1 record, so the validator and any remote prover must run within the trusted TEE boundary.

Existing validator databases must be set up again because old rows do not contain the client ciphertext.

Closes #2385.

Changelog

[[entry]]
scope = "validator"
impact = "changed"
description = "The validator stores sealed transaction inputs only after all validation checks pass."

[[entry]]
scope = "validator"
impact = "migration"
description = "Existing validator databases must be set up again for the new validated transaction record."