feat: implement room voice chat and update project documentation

[Atanu2k4]

Summary

This PR introduces the new room voice chat functionality with media and Picture-in-Picture (PiP) support. It also updates the documentation to reflect recent infrastructure changes, including the transition to Mailjet for transactional emails and new deployment instructions for Railway.

Related issue

Fixes #72

Changes

• Implemented room voice chat page with media, PiP, and state management
• Updated README environment variables and instructions for Mailjet integration (replacing SMTP/Nodemailer)
• Added Railway deployment guide as the recommended deployment method
• Expanded the project directory structure details in the documentation to reflect the current app layout
• Added Sonner for toast notifications and Lucide React for UI icons

Testing

• Verified room voice chat connections and media stream stability
• Tested Picture-in-Picture functionality during active calls
• Reviewed README instructions for clarity and accuracy

Checklist

• Title follows the repository PR format
• The issue is linked with Fixes #72
• Testing notes are included

[github-actions]

✅ PR Validation Passed

Your PR title and description meet all requirements:

• Title follows conventional format
• All required sections are present
• Issue is properly linked (Room UI #72)