[Architecture][P0] Fix Provider Layer Data Model Violations

[AustinChangLinksys]

🎯 Goal

Remove all direct references to core/jnap/models/ from Provider layer, following the 4-layer architecture principle.

📁 Affected Files (5)

File	Violating Model	Priority
auto_parent_first_login_provider.dart	FirmwareUpdateSettings	High
add_nodes_provider.dart	BackHaulInfoData	High
add_wired_nodes_provider.dart	BackHaulInfoData	High
pnp_provider.dart	AutoConfigurationSettings	High
mock_pnp_providers.dart	AutoConfigurationSettings	Medium

✅ Acceptance Criteria

grep -r "import 'package:privacy_gui/core/jnap/models/" lib/page/*/providers/*.dart
# Expected: 0 results

📋 Task List

• Create Service layer for auto_parent_first_login_provider
• Create BackhaulInfoUI model for add_nodes_provider
• Reuse backhaul solution for add_wired_nodes_provider
• Modify pnp_provider to use UI models
• Update mock_pnp_providers to sync with new types

Parent: #549