feat: chat pagination — infinite scroll / load older messages

- Backend: cursor-based pagination via ?before=<ISO timestamp>
- Frontend: auto-load when scrolling to top (<60px), spinner + manual 'Загрузить ещё' button
- Poll merge: preserves older history when new messages arrive from polling
- hasMoreMsgs flag: shown only when exactly 50 msgs returned (more may exist)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/chat/ChatWidget.tsx

@@ -119,9 +119,11 @@ export function ChatWidget() {
   const [activeRoom, setActiveRoom]   = useState<ChatRoom | null>(null)
   const [messages, setMessages]       = useState<ChatMessage[]>([])
   const [text, setText]               = useState('')
-  const [loadingRooms, setLoadingRooms] = useState(false)
-  const [loadingMsgs, setLoadingMsgs]   = useState(false)
-  const [sending, setSending]           = useState(false)
+  const [loadingRooms, setLoadingRooms]   = useState(false)
+  const [loadingMsgs, setLoadingMsgs]     = useState(false)
+  const [loadingOlder, setLoadingOlder]   = useState(false)
+  const [hasMoreMsgs, setHasMoreMsgs]     = useState(false)
+  const [sending, setSending]             = useState(false)
   const [attachment, setAttachment]     = useState<File | null>(null)
   const [attachPreview, setAttachPreview] = useState<string | null>(null)
 
@@ -251,16 +253,22 @@ export function ChatWidget() {
     if (view !== 'messages' || !activeRoom) return
     const interval = setInterval(async () => {
       try {
-        const [msgs, typing] = await Promise.all([
+        const [fresh, typing] = await Promise.all([
           api.chat.getMessages(slug, activeRoom.id),
           api.chat.getTyping(slug, activeRoom.id),
         ])
-        if (settings.soundEnabled && msgs.length > prevMsgCountRef.current && prevMsgCountRef.current > 0) {
-          const last = msgs[msgs.length - 1]
-          if (last.senderId !== user?.id) playNotifSound()
-        }
-        prevMsgCountRef.current = msgs.length
-        setMessages(msgs)
+        setMessages(prev => {
+          // Merge: keep older history + update/append fresh messages
+          const freshIds = new Set(fresh.map(m => m.id))
+          const older = prev.filter(m => !freshIds.has(m.id) && new Date(m.createdAt) < new Date(fresh[0]?.createdAt ?? 0))
+          const merged = [...older, ...fresh]
+          if (settings.soundEnabled && merged.length > prevMsgCountRef.current && prevMsgCountRef.current > 0) {
+            const last = merged[merged.length - 1]
+            if (last.senderId !== user?.id) playNotifSound()
+          }
+          prevMsgCountRef.current = merged.length
+          return merged
+        })
         setTypingNames(typing)
       } catch { /**/ }
     }, 2000)
@@ -346,10 +354,11 @@ export function ChatWidget() {
   const openRoom = async (room: ChatRoom) => {
     setActiveRoom(room); setView('messages'); setLoadingMsgs(true)
     setRoomSearch(''); setRoomSearchOpen(false)
-    prevMsgCountRef.current = 0; isTypingRef.current = false
+    prevMsgCountRef.current = 0; isTypingRef.current = false; setHasMoreMsgs(false)
     try {
       const msgs = await api.chat.getMessages(slug, room.id)
       prevMsgCountRef.current = msgs.length
+      setHasMoreMsgs(msgs.length === 50)
       setMessages(msgs)
       await api.chat.markRead(slug, room.id)
       setRooms(prev => prev.map(r => r.id === room.id ? { ...r, unreadCount: 0 } : r))
@@ -449,10 +458,30 @@ export function ChatWidget() {
     const next = { ...settings, ...patch }; setSettings(next); saveSettings(next)
   }
 
+  const loadOlderMessages = async () => {
+    if (!activeRoom || loadingOlder || !hasMoreMsgs || messages.length === 0) return
+    const oldest = messages[0].createdAt
+    setLoadingOlder(true)
+    try {
+      const older = await api.chat.getMessages(slug, activeRoom.id, 50, oldest)
+      if (older.length === 0) { setHasMoreMsgs(false); return }
+      setHasMoreMsgs(older.length === 50)
+      // Preserve scroll position after prepending
+      const el = messagesContainerRef.current
+      const prevHeight = el?.scrollHeight ?? 0
+      setMessages(prev => [...older, ...prev])
+      requestAnimationFrame(() => {
+        if (el) el.scrollTop = el.scrollHeight - prevHeight
+      })
+    } catch { /**/ }
+    finally { setLoadingOlder(false) }
+  }
+
   const goBack = () => {
     if (view === 'messages') {
       sendTyping(false)
       setRoomSearch(''); setRoomSearchOpen(false)
+      setHasMoreMsgs(false)
       setView('rooms'); setActiveRoom(null); setEditingMsgId(null); setTypingNames([])
     }
     else if (view === 'search') { setView('rooms'); setSearchQuery('') }
@@ -657,7 +686,23 @@ export function ChatWidget() {
                   </div>
                 </div>
               )}
-              <div ref={messagesContainerRef} className="flex-1 overflow-y-auto px-3 py-3 space-y-2">
+              <div ref={messagesContainerRef} className="flex-1 overflow-y-auto px-3 py-3 space-y-2"
+                onScroll={e => { if ((e.target as HTMLDivElement).scrollTop < 60 && hasMoreMsgs && !loadingOlder) void loadOlderMessages() }}>
+                {/* Load more older messages */}
+                {hasMoreMsgs && !loadingOlder && (
+                  <div className="flex justify-center pt-1 pb-2">
+                    <button onClick={() => void loadOlderMessages()}
+                      className="text-xs text-brand-600 hover:text-brand-700 hover:underline transition-colors">
+                      Загрузить ещё
+                    </button>
+                  </div>
+                )}
+                {loadingOlder && (
+                  <div className="flex justify-center py-2">
+                    <Loader2 size={14} className="animate-spin text-slate-400" />
+                  </div>
+                )}
+
                 {loadingMsgs ? (
                   <div className="flex items-center justify-center h-32"><Loader2 size={20} className="animate-spin text-slate-400" /></div>
                 ) : messages.length === 0 ? (

src/lib/api.ts

@@ -333,8 +333,10 @@ export const api = {
   chat: {
     listRooms: (slug: string) =>
       req<ChatRoom[]>('GET', `/api/hotels/${slug}/chat/rooms`),
-    getMessages: (slug: string, roomId: string, limit = 50) =>
-      req<ChatMessage[]>('GET', `/api/hotels/${slug}/chat/rooms/${roomId}/messages?limit=${limit}`),
+    getMessages: (slug: string, roomId: string, limit = 50, before?: string) => {
+      const qs = before ? `?limit=${limit}&before=${encodeURIComponent(before)}` : `?limit=${limit}`
+      return req<ChatMessage[]>('GET', `/api/hotels/${slug}/chat/rooms/${roomId}/messages${qs}`)
+    },
     sendMessage: (slug: string, roomId: string, text: string, attachmentUrl?: string) =>
       req<ChatMessage>('POST', `/api/hotels/${slug}/chat/rooms/${roomId}/messages`, { text, ...(attachmentUrl ? { attachment_url: attachmentUrl } : {}) }),
     uploadImage: async (file: File): Promise<{ url: string }> => {