Add systemd timer deployment for scheduled ingestion cycle

- deploy/goodnews.service: oneshot unit running 'goodnews cycle' with a
  generous TimeoutStartSec so long classify runs are not killed.
- deploy/goodnews.timer: every 15 min, Persistent=true to catch missed runs.
- deploy/goodnews.env.example: LLM endpoint + DB path for the scheduled run.
- README: scheduling/install docs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

deploy/goodnews.timer

@@ -0,0 +1,15 @@
+[Unit]
+Description=Run the goodNews ingestion cycle periodically
+
+[Timer]
+# First run shortly after boot, then every 15 minutes. Per-source
+# poll_interval_minutes still governs which feeds are actually hit each tick.
+OnBootSec=2min
+OnUnitActiveSec=15min
+# Catch up a missed run if the machine was off when one was due.
+Persistent=true
+AccuracySec=1min
+Unit=goodnews.service
+
+[Install]
+WantedBy=timers.target