Fix: Leaflet lokal hosten + Container-Hoehe explizit setzen

- Leaflet JS/CSS + MarkerCluster lokal in /static/vendor/ (kein CDN)
- Marker-Images lokal gehostet
- Container-Hoehe wird per JS berechnet falls gridstack 0px liefert
- gridstack karte-Item: display flex auf item-content
- Kein CDN-Abhaengigkeit mehr fuer Kartenfeature

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/static/vendor/MarkerCluster.css

@@ -0,0 +1,14 @@
+.leaflet-cluster-anim .leaflet-marker-icon, .leaflet-cluster-anim .leaflet-marker-shadow {
+	-webkit-transition: -webkit-transform 0.3s ease-out, opacity 0.3s ease-in;
+	-moz-transition: -moz-transform 0.3s ease-out, opacity 0.3s ease-in;
+	-o-transition: -o-transform 0.3s ease-out, opacity 0.3s ease-in;
+	transition: transform 0.3s ease-out, opacity 0.3s ease-in;
+}
+
+.leaflet-cluster-spider-leg {
+	/* stroke-dashoffset (duration and function) should match with leaflet-marker-icon transform in order to track it exactly */
+	-webkit-transition: -webkit-stroke-dashoffset 0.3s ease-out, -webkit-stroke-opacity 0.3s ease-in;
+	-moz-transition: -moz-stroke-dashoffset 0.3s ease-out, -moz-stroke-opacity 0.3s ease-in;
+	-o-transition: -o-stroke-dashoffset 0.3s ease-out, -o-stroke-opacity 0.3s ease-in;
+	transition: stroke-dashoffset 0.3s ease-out, stroke-opacity 0.3s ease-in;
+}