Add 'read up to here' marker line in chat messages

frontend/src/components/Chat/MessageList.tsx

@@ -5,6 +5,7 @@ import CodeBlock from '../common/CodeBlock';
 import { useAuth } from '../../contexts/AuthContext';
 import { useToast } from '../../contexts/ToastContext';
 import { useUserStatus } from '../../contexts/UserStatusContext';
+import { useUnreadMessages } from '../../contexts/UnreadMessagesContext';
 import UserStatusIndicator from '../common/UserStatusIndicator';
 
 interface MessageListProps {
@@ -16,6 +17,7 @@ const MessageList: React.FC<MessageListProps> = ({ channelId, onReply }) => {
   const { user } = useAuth();
   const { addToast } = useToast();
   const { getUserStatus } = useUserStatus();
+  const { getLastReadTimestamp } = useUnreadMessages();
   const [messages, setMessages] = useState<Message[]>([]);
   const [loading, setLoading] = useState(true);
   const [hasMore, setHasMore] = useState(true);
@@ -272,6 +274,23 @@ const MessageList: React.FC<MessageListProps> = ({ channelId, onReply }) => {
           <span className="text-xs text-gray-500 dark:text-gray-400">Lade ältere Nachrichten...</span>
         </div>
       )}
+      {(() => {
+        const lastReadTimestamp = getLastReadTimestamp('channel', channelId);
+        const hasUnreadMessages = messages.some(msg => {
+          const messageDate = new Date(msg.created_at);
+          return lastReadTimestamp && messageDate > lastReadTimestamp;
+        });
+        
+        return hasUnreadMessages ? (
+          <div className="flex items-center my-4">
+            <div className="flex-1 border-t border-gray-300 dark:border-gray-600"></div>
+            <div className="px-3 py-1 bg-gray-100 dark:bg-gray-700 rounded-full text-xs text-gray-600 dark:text-gray-300 border border-gray-300 dark:border-gray-600">
+              Gelesen bis hier
+            </div>
+            <div className="flex-1 border-t border-gray-300 dark:border-gray-600"></div>
+          </div>
+        ) : null;
+      })()}
       {messages.map((message) => {
         const isOwnMessage = user && message.sender_id === user.id;
         

frontend/src/contexts/UnreadMessagesContext.tsx

@@ -6,6 +6,7 @@ interface UnreadMessagesContextType {
   unreadDirectMessages: Set<number>;
   activeChannelId: number | null;
   activeDirectMessageUserId: number | null;
+  lastReadTimestamps: { [key: string]: Date }; // 'channel-{id}' or 'dm-{userId}' => timestamp
   markChannelAsRead: (channelId: number) => void;
   markChannelAsUnread: (channelId: number) => void;
   markDirectMessageAsRead: (userId: number) => void;
@@ -14,6 +15,7 @@ interface UnreadMessagesContextType {
   hasUnreadDirectMessage: (userId: number) => boolean;
   setActiveChannel: (channelId: number | null) => void;
   setActiveDirectMessage: (userId: number | null) => void;
+  getLastReadTimestamp: (type: 'channel' | 'dm', id: number) => Date | null;
 }
 
 const UnreadMessagesContext = createContext<UnreadMessagesContextType | undefined>(undefined);
@@ -35,6 +37,7 @@ export const UnreadMessagesProvider: React.FC<UnreadMessagesProviderProps> = ({
   const [unreadDirectMessages, setUnreadDirectMessages] = useState<Set<number>>(new Set());
   const [activeChannelId, setActiveChannelId] = useState<number | null>(null);
   const [activeDirectMessageUserId, setActiveDirectMessageUserId] = useState<number | null>(null);
+  const [lastReadTimestamps, setLastReadTimestamps] = useState<{ [key: string]: Date }>({});
   const { user } = useAuth();
 
   // Listen for unread message events from the presence WebSocket
@@ -87,10 +90,24 @@ export const UnreadMessagesProvider: React.FC<UnreadMessagesProviderProps> = ({
 
   const setActiveChannel = (channelId: number | null) => {
     setActiveChannelId(channelId);
+    if (channelId !== null) {
+      // Set timestamp when channel becomes active
+      setLastReadTimestamps(prev => ({
+        ...prev,
+        [`channel-${channelId}`]: new Date()
+      }));
+    }
   };
 
   const setActiveDirectMessage = (userId: number | null) => {
     setActiveDirectMessageUserId(userId);
+    if (userId !== null) {
+      // Set timestamp when DM becomes active
+      setLastReadTimestamps(prev => ({
+        ...prev,
+        [`dm-${userId}`]: new Date()
+      }));
+    }
   };
 
   const hasUnreadChannel = (channelId: number) => {
@@ -101,6 +118,11 @@ export const UnreadMessagesProvider: React.FC<UnreadMessagesProviderProps> = ({
     return unreadDirectMessages.has(userId);
   };
 
+  const getLastReadTimestamp = (type: 'channel' | 'dm', id: number): Date | null => {
+    const key = `${type}-${id}`;
+    return lastReadTimestamps[key] || null;
+  };
+
   return (
     <UnreadMessagesContext.Provider
       value={{
@@ -108,6 +130,7 @@ export const UnreadMessagesProvider: React.FC<UnreadMessagesProviderProps> = ({
         unreadDirectMessages,
         activeChannelId,
         activeDirectMessageUserId,
+        lastReadTimestamps,
         markChannelAsRead,
         markChannelAsUnread,
         markDirectMessageAsRead,
@@ -116,6 +139,7 @@ export const UnreadMessagesProvider: React.FC<UnreadMessagesProviderProps> = ({
         hasUnreadDirectMessage,
         setActiveChannel,
         setActiveDirectMessage,
+        getLastReadTimestamp,
       }}
     >
       {children}