Improve reconnection and restoration

Fixed automatic subscription restoration for clients reconnecting with known serial numbers. This critical feature now works correctly, eliminating the need for manual re-subscription after power cycles or resets.

💡 Key Features Implemented
✅ Automatic Subscription Restoration - No manual re-subscription needed
✅ Topic Name Preservation - Full names stored and restored
✅ Zero-Touch Reconnection - Complete transparency for users
✅ Flash Storage - Everything persists across power cycles