Adds a --init mode that seeds the database with past shows from a given
anchor episode/date forward, batch-fetching likes from SoundCloud and
partitioning them into weekly buckets. Episode numbers are tracked in
the shows table and auto-incremented by the poller for new shows.
Includes full API documentation (docs/api.md) and updated README.
Made-with: Cursor
Nick is the host; if he unlikes a track, the service should respect
that and remove it from the show playlist. Positions re-compact after
removal. The tracks table retains the record for historical reference.
Made-with: Cursor
