fix: update verified_at when PDS resolution fails in reconciler
did:web docs (and any DID with unresolvable PDS) stayed at
verified_at=NULL forever, permanently clogging the front of the
reconciler queue. Now they get pushed to the back with the normal
7-day reverify window.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>