v0.9.19 - pull source successor (talkhard)

The weekly pull source moved: walksoftly retired, talkhard succeeds it.

Fixed

• The default weekly-pull source (pull_source_url) pointed at the retired
  walksoftly.itsaninja.party host (dead with HTTP 523 since at least
  2026-07-20; upstream retired it 2026-05 per the Mylar community fork). The
  default now points at its successor, talkhard.notaninja.party, same API
  contract. Existing installs that never overrode the setting pick the new
  default up on upgrade; an explicit pull_source_url in config.yaml is
  honored unchanged. (FRG-PULL-002)