[Architecture][P2] Decouple dashboard → health_check Dependency

[AustinChangLinksys]

🎯 Goal

Remove direct dependency of dashboard_home_provider on health_check_provider.

📁 Affected Files

File	Coupling Type	Risk
dashboard_home_provider.dart	ref.watch(healthCheckProvider)	🔴 High

💡 Suggested Solution

// Solution: Extract HealthCheck results to shared layer
// lib/providers/network_health_provider.dart
final networkHealthProvider = Provider<NetworkHealthState>((ref) {
  final speedTestResult = ref.watch(_speedTestResultProvider);
  return NetworkHealthState(lastSpeedTest: speedTestResult);
});

✅ Acceptance Criteria

• dashboard_home_provider.dart no longer imports health_check_provider
• Create lib/providers/network_health_provider.dart as shared layer

Parent: #549