Show HN: Let's Seal – Let's Encrypt for document signing, free and self-hosted

Let's Seal is a free, open-source platform that provides document signing and verification services—positioning itself as "Let's Encrypt for document sealing." It uses the SEAL standard (Sealed Evidence Anchored to a Ledger) to cryptographically prove that files are unaltered, issued by a known certificate, and existed by a specific date, with verification anchored to Bitcoin through OpenTimestamps. The service is available as a hosted web app, command-line tool, REST API, and self-hosted option, with all verification always remaining free and requiring no account.