map debug + coord backfill, remove email channel, countdown label

- Surface "X/Y passende Wohnungen mit Koordinaten" on the Karte view +
  admin-only "Koordinaten nachladen" button (POST /actions/backfill-coords)
  that geocodes missing flats via Google Maps directly from the web container
- Add googlemaps dep + GMAPS_API_KEY env to web service
- Light console.log in map.js ("rendering N/M markers", "building Leaflet…")
  so the browser DevTools shows what's happening
- Drop e-mail channel from notifications UI, notify dispatcher, and _alert_status;
  coerce legacy 'email' channel rows back to 'ui' on save
- Countdown said "Aktualisierung läuft…" next to "nächste Aktualisierung" →
  shortened to "aktualisiere…"

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -28,6 +28,7 @@ services:
       - SMTP_PASSWORD=${SMTP_PASSWORD:-}
       - SMTP_FROM=${SMTP_FROM:-lazyflat@localhost}
       - SMTP_STARTTLS=${SMTP_STARTTLS:-true}
+      - GMAPS_API_KEY=${GMAPS_API_KEY:-}
     volumes:
       - lazyflat_data:/data
     expose: