Initial commit — DRB server stack

Includes c2-core (FastAPI/MQTT/Firestore), discord-bot (slash commands),
frontend (Next.js admin UI), and mosquitto config.

drb-frontend/lib/useNodes.ts

@@ -0,0 +1,48 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { collection, onSnapshot, query, FirestoreError } from "firebase/firestore";
+import { onAuthStateChanged } from "firebase/auth";
+import { db, auth } from "@/lib/firebase";
+import type { NodeRecord } from "@/lib/types";
+
+export function useNodes() {
+  const [nodes, setNodes] = useState<NodeRecord[]>([]);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    let unsubFirestore: (() => void) | undefined;
+
+    const unsubAuth = onAuthStateChanged(auth, (user) => {
+      if (unsubFirestore) { unsubFirestore(); unsubFirestore = undefined; }
+
+      if (!user) {
+        setNodes([]);
+        setLoading(false);
+        return;
+      }
+
+      const q = query(collection(db, "nodes"));
+      unsubFirestore = onSnapshot(q, (snap) => {
+        setNodes(snap.docs.map((d) => d.data() as NodeRecord));
+        setLoading(false);
+      }, (err: FirestoreError) => { console.error("useNodes:", err); setError(err.message); setLoading(false); });
+    });
+
+    return () => {
+      unsubAuth();
+      if (unsubFirestore) unsubFirestore();
+    };
+  }, []);
+
+  return { nodes, loading, error };
+}
+
+export function useUnconfiguredNodes() {
+  const { nodes, loading } = useNodes();
+  return {
+    nodes: nodes.filter((n) => !n.configured),
+    loading,
+  };
+}