map view (Leaflet + OSM), iOS switches, Alarm → Benachrichtigungen

* flats: new lat/lng columns (migration v3); alert geocodes every new flat
  through googlemaps and ships coords in the payload
* web: CSP extended for unpkg (leaflet.css) + tile.openstreetmap.org
* Wohnungen tab: Liste/Karte view toggle (segmented, CSS-only via :has(),
  selection persisted in localStorage). Karte shows passende flats as Pins
  on an OSM tile map; Popup per Pin mit Adresse, Zimmer/m²/€ und Link
* Top-strip toggles are now proper iOS-style toggle switches (single
  rounded knob sliding in a pill, red when on), no descriptive subtitle
* Alarm-Karte verlinkt jetzt auf /einstellungen/benachrichtigungen
  (Filter-Karte bleibt /einstellungen/filter)

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

alert/main.py

@@ -32,6 +32,7 @@ class FlatAlerter:
 
     def _flat_payload(self, flat: Flat) -> dict:
         c = flat.connectivity
+        lat, lng = flat.coords
         return {
             "id": flat.id,
             "link": flat.link,
@@ -53,6 +54,8 @@ class FlatAlerter:
             "energy_value": flat.energy_value,
             "energy_certificate": flat.energy_certificate,
             "address_link_gmaps": flat.address_link_gmaps,
+            "lat": lat,
+            "lng": lng,
             "connectivity": {
                 "morning_time": c.get("morning_time", 0),
                 "morning_transfers": c.get("morning_transfers", 0),