feat(windkarte): permanente 2km/5km-Ringe togglebar in Legende

Zeigt 2km (indigo) und 5km (lila) Pufferringe für alle Gebiete gleichzeitig,
unabhängig von Selektion. Default versteckt, Klick auf Legendenitem ein-/ausblenden.

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

src/lib/components/WindkarteMap.svelte

@@ -9,12 +9,14 @@
     onready = null,
     initialGebietsNr = null,
     hiddenStatuses = [],
+    hiddenRings = ["2km", "5km"],
   }: {
     areas: WindArea[];
     onselect: (area: WindArea | null, center: [number, number] | null) => void;
     onready?: ((ctrl: { reset: () => void }) => void) | null;
     initialGebietsNr?: string | null;
     hiddenStatuses?: string[];
+    hiddenRings?: string[];
   } = $props();
 
   // Mirror prop into plain variable so Leaflet event handlers read current value.
@@ -46,6 +48,20 @@
   let selectedSlug = $state<string | null>(null);
   let geojsonLayer: import("leaflet").GeoJSON | null = null;
   let buffering = $state(false);
+  let permanentRing2km = $state<import("leaflet").LayerGroup | null>(null);
+  let permanentRing5km = $state<import("leaflet").LayerGroup | null>(null);
+
+  $effect(() => {
+    const hidden = hiddenRings;
+    for (const [key, layer] of [["2km", permanentRing2km], ["5km", permanentRing5km]] as [string, import("leaflet").LayerGroup | null][]) {
+      if (!layer || !map) continue;
+      if (hidden.includes(key)) {
+        if (map.hasLayer(layer)) map.removeLayer(layer);
+      } else {
+        if (!map.hasLayer(layer)) map.addLayer(layer);
+      }
+    }
+  });
 
   const COLORS: Record<string, { fill: string; stroke: string }> = {
     rechtskraeftig:           { fill: "#2d7a45", stroke: "#1a4d28" },
@@ -258,6 +274,19 @@
       map.on("zoomend", syncLabels);
       syncLabels();
 
+      // Permanent 2km / 5km rings for all areas (built async, shown/hidden via hiddenRings prop)
+      const { buffer: turfBuffer } = await import("@turf/buffer");
+      const r2 = L.layerGroup();
+      const r5 = L.layerGroup();
+      for (const feature of geo.features) {
+        const b2 = turfBuffer(feature, 2, { units: "kilometers" });
+        if (b2) L.geoJSON(b2, { style: { color: "#5e6fa3", fillColor: "#5e6fa3", fillOpacity: 0.04, weight: 1.5, dashArray: "10 5" }, interactive: false }).addTo(r2);
+        const b5 = turfBuffer(feature, 5, { units: "kilometers" });
+        if (b5) L.geoJSON(b5, { style: { color: "#8a567a", fillColor: "#8a567a", fillOpacity: 0.03, weight: 1.5, dashArray: "14 6" }, interactive: false }).addTo(r5);
+      }
+      permanentRing2km = r2;
+      permanentRing5km = r5;
+
       // Auto-select from hash
       if (initialGebietsNr) {
         const entry = layerMap.get(initialGebietsNr);