centralize message validation flow

[ash1shkumar]

📝 Description

This PR refactors the messaging request-processing flow by centralizing payload validation through a reusable validation utility. Previously, message validation rules were implemented directly inside the controller, increasing coupling between request handling and validation responsibilities.

The updated implementation delegates validation to a dedicated helper, resulting in a cleaner controller structure and a more maintainable validation workflow.

Key Improvements

• Integrated centralized message validation utility into the messaging controller
• Removed inline validation logic from request-processing flow
• Improved separation of concerns between validation and business logic
• Reduced controller complexity and duplicated validation responsibilities
• Established a reusable foundation for future message format validations
• Improved maintainability and consistency across messaging workflows

Impact

This refactor strengthens the messaging architecture by ensuring validation logic remains centralized and reusable. Future validation enhancements can now be implemented in a single location without modifying controller behavior.

🎯 Type of Change

• ♻️ Refactoring
• 🛡️ Code Quality Improvement

✅ Testing

• Verified valid text messages are processed successfully
• Verified invalid payloads return appropriate validation errors
• Verified authentication flow remains unchanged
• Verified image and audio message validation behavior remains intact
• Confirmed message creation and realtime event emission continue functioning correctly

Fixes #218

Expected Labels

level3 `NSoC'26

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