Improve chat replies, hubs API & UI

Backend: enrich message reply data (include created_at and media_files) and ensure chat owners are treated as members; tighten/extend permission checks and message query filters; fix hub routers so moderators/tags routes are resolved before hub detail; accept hub id from request.data in hub permission/tag views; add PostHub serializer and expose hub_detail on posts.

Frontend: update generated API models (postHub, replyTo, members_detail, hub_detail); add hub-related pages/routes and components (HubCard, HubHeader, Tags) and a hub posts feed hook; rework message UI and composer to show richer reply previews (media thumbnails, timestamps), adjust video preload to metadata; add tag selection UI to PostComposer and wire hub tags fetching.

Also: minor UI/UX improvements and generated model exports updated to match backend changes.

frontend/src/pages/social/chat/ChatRoomPage.tsx

@@ -317,7 +317,7 @@ export default function ChatRoomPage() {
         )}
 
         {/* Beginning-of-chat banner — shown only once all pages are confirmed loaded */}
-        {!hasNextPage && !isLoading && messages.length > 0 && chat && (
+        {!hasNextPage && !isLoading && chat && (
           <div className="flex flex-col items-center gap-3 px-6 py-10 text-center">
             <Avatar
               name={chat.name ?? `Chat ${chatId}`}