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>

web/geocode.py

@@ -0,0 +1,46 @@
+"""Thin Google-Maps geocoding wrapper used only for the admin coord backfill.
+
+Runtime geocoding during scraping happens in the alert service. This module
+exists so the web service can lazy-fix flats that were scraped before the
+lat/lng migration (or where the alert run skipped geocoding).
+"""
+import logging
+from typing import Optional
+
+from settings import GMAPS_API_KEY
+
+logger = logging.getLogger("web.geocode")
+
+_client = None
+
+
+def _get_client():
+    global _client
+    if _client is not None:
+        return _client
+    if not GMAPS_API_KEY:
+        return None
+    try:
+        import googlemaps
+        _client = googlemaps.Client(key=GMAPS_API_KEY)
+        return _client
+    except Exception as e:
+        logger.warning("googlemaps client init failed: %s", e)
+        return None
+
+
+def geocode(address: str) -> Optional[tuple[float, float]]:
+    if not address:
+        return None
+    gm = _get_client()
+    if gm is None:
+        return None
+    try:
+        res = gm.geocode(f"{address}, Berlin, Germany")
+        if not res:
+            return None
+        loc = res[0]["geometry"]["location"]
+        return float(loc["lat"]), float(loc["lng"])
+    except Exception as e:
+        logger.warning("geocode failed for %r: %s", address, e)
+        return None