Refactor: Remove automatic "Mark as Read" from chat history fetch

[Copilot]

Messages were automatically marked as read when fetching chat history via getChatHistoryForAnonymous, preventing users from previewing chats without clearing unread counts. The frontend should control when messages are marked read via the MARK_AS_READ WebSocket message.

Changes

• ChatService.getChatHistoryForAnonymous: Removed markMessagesAsRead() call, changed to @Transactional(readOnly = true)
• MessagingService.setMessageAsRead: Now requires user email for proper authorization

  public void setMessageAsRead(String email, String sessionId) {
      User user = userRepository.findByEmail(email)
              .orElseThrow(() -> new RuntimeException("User not found: " + email));
      chatMessageRepository.markMessagesAsRead(user.getId(), sessionId);
  }

• ChatWebSocketHandler: MARK_AS_READ handler extracts user from JWT and validates both email and chatId before processing
• ChatMessageRepository: Removed unused markMessagesAsRead(String sessionId) overload that lacked user scoping

Tests

Added ChatServiceTest and MessagingServiceTest to verify:

• getChatHistoryForAnonymous no longer calls markMessagesAsRead
• setMessageAsRead correctly scopes updates to user + session

Original prompt

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This section details on the original issue you should resolve

<issue_title>Refactor: "Mark as Read" Logic is Automatic and Inflexible</issue_title>
<issue_description>### Description
Currently, messages are marked as read in two places:

1. Automatically when an anonymous user (or a user) calls getChatHistoryForAnonymous. This is bad UX, as the user may just be previewing the chat, not reading it.
2. Via a MARK_AS_READ WebSocket message type.

The first method should be removed in favor of the second, which gives the frontend control over when a chat is marked as read.

Acceptance Criteria

1. Remove the chatMessageRepository.markMessagesAsRead(recipient.getId(), sessionId); line from ChatService.getChatHistoryForAnonymous.
2. Ensure the MARK_AS_READ case in ChatWebSocketHandler.handleTextMessage correctly uses the payload.getChatId() (which seems to be the sessionId) to mark messages as read.
3. The ChatService.getUserChatSessions method, which calculates unreadCount, will now correctly reflect the true unread count until the user's client sends the MARK_AS_READ message.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Refactor: "Mark as Read" Logic is Automatic and Inflexible #8

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