🚚(frontend) move participant list code into a feature folder

Reorganize all participant list related code elements into a
dedicated feature folder, so related components, hooks and helpers
are grouped together and easier to locate.

src/frontend/src/features/participants/api/lowerHandParticipants.ts

@@ -0,0 +1,21 @@
+import type { Participant } from 'livekit-client'
+import { useLowerHandParticipant } from './lowerHandParticipant'
+
+export const useLowerHandParticipants = () => {
+  const { lowerHandParticipant } = useLowerHandParticipant()
+
+  const lowerHandParticipants = (participants: Array<Participant>) => {
+    try {
+      const promises = participants.map((participant) =>
+        lowerHandParticipant(participant)
+      )
+      return Promise.all(promises)
+    } catch (error) {
+      console.error('An error occurred while lowering hands :', error)
+      throw new Error('An error occurred while lowering hands.', {
+        cause: error,
+      })
+    }
+  }
+  return { lowerHandParticipants }
+}