feat: add VegetationSystem with InstancedMesh rendering

src/world/vegetation/VegetationSystem.tsx

@@ -0,0 +1,42 @@
+import { Suspense } from "react";
+import { InstancedVegetation } from "@/world/vegetation/InstancedVegetation";
+import { useVegetationData } from "@/world/vegetation/useVegetationData";
+import {
+  VEGETATION_TYPES,
+  type VegetationType,
+} from "@/world/vegetation/vegetationConfig";
+
+export function VegetationSystem(): React.JSX.Element | null {
+  const { data, isLoading } = useVegetationData();
+
+  if (isLoading || !data) {
+    return null;
+  }
+
+  const enabledTypes = Object.entries(VEGETATION_TYPES).filter(
+    ([, config]) => config.enabled,
+  );
+
+  return (
+    <group name="vegetation-system">
+      {enabledTypes.map(([type, config]) => {
+        const instances = data.get(type as VegetationType);
+
+        if (!instances || instances.length === 0) {
+          return null;
+        }
+
+        return (
+          <Suspense key={type} fallback={null}>
+            <InstancedVegetation
+              modelPath={config.modelPath}
+              instances={instances}
+              castShadow={config.castShadow}
+              receiveShadow={config.receiveShadow}
+            />
+          </Suspense>
+        );
+      })}
+    </group>
+  );
+}