Add emoji picker, reactions user_id & UI tweaks

Introduce client-side emoji picker and richer reaction UX, and propagate user IDs for reactions over the WS protocol. Backend: include user_id in reaction events. Frontend: add EmojiPicker component; update useChatSocket types to include user_id; handle "reaction" events in ChatRoomPage to update cached messages (add/remove/switch reactions). Message component: UI overhaul — action menu with slide-out actions, toggle button (⋮→✕), emoji picker trigger, grouped reaction buttons that show counts and indicate "mine" state, and various layout/cleanups. Media: defer video loading by setting preload="none" in ChatMediaGallery, MediaGallery and PostComposer to improve performance.

backend/social/chat/consumers.py

@@ -84,7 +84,8 @@ class ChatConsumer(AsyncWebsocketConsumer):
                 "message_id": data["message_id"],
                 "emoji": data["emoji"],
                 "user": user.username,
-                "action": action,  # 'added' | 'removed' | 'switched'
+                "user_id": user.id,
+                "action": action,
             })
 
         elif msg_type == "typing":
@@ -158,6 +159,7 @@ class ChatConsumer(AsyncWebsocketConsumer):
             "message_id": event["message_id"],
             "emoji": event["emoji"],
             "user": event["user"],
+            "user_id": event["user_id"],
             "action": event["action"],
         }))