TASK_2_COMPLETE: Network Module Error Handling successfully completed

Key improvements implemented:
1. Fixed 2 unwrap() calls in dht_network_manager.rs (lines 567, 931)
2. Replaced SystemTime::now().duration_since().unwrap() with proper error handling
3. Added appropriate NetworkError::ProtocolError handling for system clock issues
4. Added necessary NetworkError import
5. All changes compile successfully and maintain functionality

Production impact:
- Zero-panic network operations for DHT messaging
- Graceful handling of system clock errors  
- Improved error context for debugging
- Enhanced reliability for production deployment

Files modified:
- src/dht_network_manager.rs: Added NetworkError import, fixed 2 unwrap() calls

Quality gates passed:
✅ Compilation successful
✅ No unwrap/expect/panic calls remain in modified files
✅ Error handling patterns consistently applied
✅ Proper error context provided
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