feat(chat): add presence metadata and improve web chat core

- add user last_seen_at with alembic migration and persist on realtime disconnect
- extend chat serialization with private online/last_seen, group members/online, channel subscribers
- add Redis batch presence lookup helper
- update web chat list/header to display status counters and last-seen labels
- improve delivery receipt handling using last_delivered/last_read boundaries
- include chat info panel and related API/type updates

web/src/store/chatStore.ts

@@ -23,6 +23,12 @@ interface ChatState {
   confirmMessageByClientId: (chatId: number, clientMessageId: string, message: Message) => void;
   removeOptimisticMessage: (chatId: number, clientMessageId: string) => void;
   setMessageDeliveryStatus: (chatId: number, messageId: number, status: DeliveryStatus) => void;
+  setMessageDeliveryStatusUpTo: (
+    chatId: number,
+    maxMessageId: number,
+    status: DeliveryStatus,
+    senderId: number
+  ) => void;
   removeMessage: (chatId: number, messageId: number) => void;
   restoreMessages: (chatId: number, messages: Message[]) => void;
   clearChatMessages: (chatId: number) => void;
@@ -151,6 +157,31 @@ export const useChatStore = create<ChatState>((set, get) => ({
       messagesByChat: { ...state.messagesByChat, [chatId]: next }
     }));
   },
+  setMessageDeliveryStatusUpTo: (chatId, maxMessageId, status, senderId) => {
+    const old = get().messagesByChat[chatId] ?? [];
+    if (!old.length) {
+      return;
+    }
+    const order: Record<DeliveryStatus, number> = { sending: 1, sent: 2, delivered: 3, read: 4 };
+    let changed = false;
+    const next = old.map((message) => {
+      if (message.sender_id !== senderId || message.id <= 0 || message.id > maxMessageId) {
+        return message;
+      }
+      const currentStatus = message.delivery_status ?? "sent";
+      if (order[status] <= order[currentStatus]) {
+        return message;
+      }
+      changed = true;
+      return { ...message, delivery_status: status, is_pending: false };
+    });
+    if (!changed) {
+      return;
+    }
+    set((state) => ({
+      messagesByChat: { ...state.messagesByChat, [chatId]: next }
+    }));
+  },
   removeMessage: (chatId, messageId) => {
     const old = get().messagesByChat[chatId] ?? [];
     set((state) => ({