houses: nightly Kamernet + Vesteda scraper, dedupe by address, owner-only /trackers/houses

- scripts/house-scrape.ts: polite nightly scrape (honest UA, 6-10 s apart, stops a source on 403/challenge), ingest + price history + removals, ntfy alerts on a separate topic (max 5 + summary, first run seeds)
- address_key + duplicate_of: copies on another source link to one listing, manual wins
- /projects/house-tracker -> /trackers/houses (308), owner only (404 otherwise); filters for min m2, rooms, source, Gouda region default; notes, add-by-hand form, total rent, also-on links
- scripts/house-db.sh: run the house-listing CLI as the limited house_cli role
- deploy/systemd/house-scrape.{service,timer}

deploy/systemd/house-scrape.timer

@@ -0,0 +1,10 @@
+[Unit]
+Description=House tracker scrape, once a night
+
+[Timer]
+OnCalendar=*-*-* 03:40:00 Europe/Amsterdam
+RandomizedDelaySec=1200
+Persistent=true
+
+[Install]
+WantedBy=timers.target