Improved File Synchronization Reliability and Admin Sync Control

🔄 Improvements

• Improved reliability of file and attachment synchronization by strengthening metadata handling and recovery mechanisms
• Better protection against sync interruptions and inconsistent sync state during parallel synchronization activity

🛠 Fixes

• Fixed: Potential sync state corruption caused by concurrent metadata updates
• Fixed: Recovery of attachment sync metadata from backup data when metadata files become invalid
• Fixed: Cleanup of stale synchronization sessions that could accumulate over time and affect sync stability

And other improvements