[Feature]: Verification caching task

[paralta]

Problem Statement

Currently, verification of record signatures must be performed on-demand for each query. This makes filtering by signed/trusted status expensive and slow, as each record must be verified against public keys at query time. There is no cached verification state in the database to enable efficient filtering.

Proposed Solution

Create a new reconciler task under reconciler/tasks/verification that:

1. Periodically scans records in the database that have not been verified (or need re-verification)
2. Performs signature verification against known public keys
3. Caches verification results in the database (e.g., is_signed, is_trusted, verification_timestamp)
4. Marks records for re-verification when public keys change

This enables the API to filter records by verification status efficiently without performing cryptographic operations at query time.

Alternatives Considered

No response

Additional Context

No response

Checklist

• I have read the contributing guidelines
• I have verified this does not duplicate an existing feature request