feat: replace Google tile URL hack with leaflet-google-mutant for traffic layer

Add leaflet-google-mutant@0.16.0 (exact/locked version) as a proper bridge
between the Google Maps JavaScript API and Leaflet. The old mt{s}.google.com
tile URL approach was unofficial and produced empty tiles.

Traffic layer now renders via createLayerComponent + googleMutant, loaded only
after the Maps JS API script is injected and ready (keyed off NEXT_PUBLIC_GOOGLE_MAPS_API_KEY).
Added leaflet-google-mutant to transpilePackages in next.config.mjs.

drb-frontend/components/MapView.tsx

@@ -10,7 +10,9 @@ import {
   TileLayer,
   useMap,
 } from "react-leaflet";
+import { createLayerComponent } from "@react-leaflet/core";
 import L from "leaflet";
+import "leaflet-google-mutant";
 import type { CallRecord, IncidentRecord, NodeRecord } from "@/lib/types";
 
 // ── Leaflet icon fix ──────────────────────────────────────────────────────────
@@ -145,6 +147,19 @@ function computeGroups<T extends { id: string; lat: number; lng: number }>(
   return result;
 }
 
+// ── Google Maps traffic layer via leaflet-google-mutant ───────────────────────
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const GoogleTrafficOverlay = createLayerComponent<any, object>(
+  (_props, ctx) => {
+    // leaflet-google-mutant augments L.gridLayer after the side-effect import
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const instance = (L as any).gridLayer.googleMutant({ type: "roadmap" });
+    instance.addGoogleLayer("TrafficLayer");
+    return { instance, context: ctx };
+  },
+  () => {}
+);
+
 // ── MapRefCapture — exposes L.Map instance to parent ─────────────────────────
 function MapRefCapture({ onReady }: { onReady: (m: L.Map) => void }) {
   const map = useMap();
@@ -342,6 +357,21 @@ export default function MapView({ nodes, activeCalls, incidents = [], lastUpdate
     return () => clearInterval(id);
   }, []);
 
+  // Load Google Maps JS API for leaflet-google-mutant traffic layer
+  const [googleReady, setGoogleReady] = useState(false);
+  useEffect(() => {
+    const key = process.env.NEXT_PUBLIC_GOOGLE_MAPS_API_KEY;
+    if (!key) return;
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    if ((window as any).google?.maps) { setGoogleReady(true); return; }
+    if (document.querySelector('script[src*="maps.googleapis.com/maps/api/js"]')) return;
+    const script = document.createElement("script");
+    script.src = `https://maps.googleapis.com/maps/api/js?key=${key}`;
+    script.async = true;
+    script.onload = () => setGoogleReady(true);
+    document.head.appendChild(script);
+  }, []);
+
   // Live clock for TOC situational awareness
   useEffect(() => {
     const id = setInterval(() =>
@@ -438,14 +468,9 @@ export default function MapView({ nodes, activeCalls, incidents = [], lastUpdate
             </FeatureGroup>
           </LayersControl.Overlay>
 
-          {/* Overlay: Traffic — Google Maps traffic layer */}
+          {/* Overlay: Traffic — Google Maps via leaflet-google-mutant */}
           <LayersControl.Overlay name="Traffic">
-            <TileLayer
-              url="https://mt{s}.google.com/vt?lyrs=traffic&x={x}&y={y}&z={z}"
-              subdomains={["0", "1", "2", "3"]}
-              attribution='Traffic &copy; <a href="https://maps.google.com/">Google</a>'
-              opacity={0.8}
-            />
+            {googleReady ? <GoogleTrafficOverlay /> : <FeatureGroup />}
           </LayersControl.Overlay>
 
           {/* Overlay: Weather Radar — NEXRAD via Iowa Env Mesonet; key forces remount on refresh */}

drb-frontend/next.config.mjs

@@ -1,7 +1,7 @@
 /** @type {import('next').NextConfig} */
 const nextConfig = {
   output: "standalone",
-  transpilePackages: ["leaflet", "react-leaflet"],
+  transpilePackages: ["leaflet", "react-leaflet", "leaflet-google-mutant"],
 };
 
 export default nextConfig;

drb-frontend/package.json

@@ -14,6 +14,7 @@
     "react-dom": "^18.3.0",
     "firebase": "^10.12.0",
     "leaflet": "^1.9.4",
+    "leaflet-google-mutant": "0.16.0",
     "react-leaflet": "^4.2.1"
   },
   "devDependencies": {