feat: support file and image attachments (#98)

* upload & view attachments to particles

* allow download of attachments

js/src/hooks/use-particle.ts

@@ -4,6 +4,7 @@ import {
   subscribeToParticleChildren,
   subscribeToLatestChild,
   getParticle,
+  getParticleChildren,
 } from "@/lib/firestore-particles";
 import type { Particle } from "@/api/types";
 import {
@@ -143,3 +144,16 @@ export function useParticle(path?: ParticlePath) {
     enabled: !!path,
   });
 }
+
+export function useParticleChildren(path?: ParticlePath) {
+  return useQuery({
+    queryKey: ["particle-children", path],
+    queryFn: async () => {
+      if (!path) return [];
+      const collectionPath = toFirestoreChildrenPath(path);
+      return getParticleChildren(collectionPath);
+    },
+    enabled: !!path,
+    staleTime: 1000 * 60 * 5, // 5 min — attachments don't change
+  });
+}