feat: centralize realtime message reconciliation

[ash1shkumar]

Description

Summary

This PR improves the realtime messaging architecture by consolidating socket-driven state reconciliation into reusable helper functions. Previously, multiple socket event handlers performed independent state update operations, resulting in duplicated reconciliation logic and increased maintenance complexity.

Changes Made

• Added reusable message reconciliation helpers:

  • reconcileIncomingMessage
  • reconcileSeenStatus
  • reconcileReactionUpdate
  • shouldUpdateOnlineUsers

• Refactored newMessage event handling to use centralized reconciliation logic.

• Refactored messageSeen event handling to use a shared status reconciliation helper.

• Refactored reactionUpdate event handling to use a reusable reaction reconciliation workflow.

• Refactored onlineUsers event handling to use centralized update comparison logic.

Benefits

• Reduces duplicated state reconciliation logic.
• Improves consistency across realtime event handlers.
• Simplifies future maintenance and feature additions.
• Reduces the likelihood of state drift during concurrent updates.
• Provides a cleaner foundation for scaling realtime collaboration features.

Testing

• Verified new messages are received correctly.
• Verified unread message count behavior remains unchanged.
• Verified message seen status updates correctly.
• Verified reaction updates continue to synchronize properly.
• Verified online user updates function as expected.
• Confirmed no regressions in existing chat functionality.

Fixes #203

Expected Labels

level3 NSoC'26

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