feat(mobile): add support for huddles to mobile app (#219)

* feat(mobile): add huddles with LiveKit

Mirrors the desktop huddle window: tap the headphones button on a stream
to fetch a LiveKit token from Orion and join a video room. Active huddles
show a red badge on the stream card (participant count) and a red Join
pill in the stream top bar — both driven by huddle_active_participants
synced from the LiveKit webhook.

The HuddleScreen lives at its own route (not a modal/window): video tile
grid with placeholders for camera-off, mic/camera toggles, and a leave
button. Adds the LiveKit RN SDK plus the WebRTC + LiveKit Expo config
plugins for prebuild.

https://claude.ai/code/session_01Po5tAD17MXhnqGQ9hKh6PC

* fix(mobile): exiting from huddle

* fix: pause stream during huddle

---------

Co-authored-by: Claude <[email protected]>

js/mobile/src/features/streams/StreamCard.tsx

@@ -1,5 +1,6 @@
 import { memo, useMemo } from "react";
 import { Pressable, Text, View } from "react-native";
+import { Headphones } from "lucide-react-native";
 import type { Particle, StreamProperties } from "@/api/types";
 import { isParticleDeleted } from "@/api/types";
 import { RelativeTimestamp } from "@/components/RelativeTimestamp";
@@ -147,7 +148,14 @@ export const StreamCard = memo(function StreamCard({
             )}
           />
         ) : null}
-        {isUnseen ? (
+        {(particle.huddle_active_participants?.length ?? 0) > 0 ? (
+          <View className="flex-row items-center gap-1 rounded-full bg-red-500/15 px-1.5 py-0.5">
+            <Headphones color="#ef4444" size={11} />
+            <Text className="text-red-500 text-[10px] font-semibold">
+              {particle.huddle_active_participants?.length}
+            </Text>
+          </View>
+        ) : isUnseen ? (
           <View className="bg-primary h-2 w-2 rounded-full" />
         ) : null}
       </View>