feat: Add NordVPN NordLynx (WireGuard) integration

[PedroLiu1999]

Description

This PR introduces comprehensive support for NordVPN outbounds using the WireGuard (NordLynx) protocol. It enables users to easily route traffic through NordVPN servers directly from the 3x-ui panel.

Key Features

• Integrated NordVPN Service: A new backend service (NordService) for interacting with NordVPN APIs.
• API v2 Integration: Uses the latest NordVPN API for real-time server discovery, load information, and intelligent sorting (lowest load first).
• Authentication Modes:
  • Access Token: Simplified login using a NordVPN access token to automatically retrieve credentials.
  • Private Key: Support for manual private key entry for advanced users.
• Frontend Refinements:
  • Dedicated NordVPN modal with server load indicators.
  • Automated server selection and configuration generation.
  • Proactive "Logout/Cleanup" that removes orphaned outbounds and routing rules.
• Advanced Routing:
  • Direct integration into the "Basics" settings for easy routing rule creation.
  • Individual tags for each NordVPN server (nord-<hostname>) for precise traffic control.
• Multi-language Support: Full localization in English, Farsi, and Chinese.

Changes

Backend

• [NEW] web/service/nord.go: Core logic for NordVPN API interaction.
• web/controller/xray_setting.go: Endpoints for server fetching and credential management.
• web/service/setting.go: Storage and retrieval of NordVPN configuration.

Frontend

• [NEW] web/html/modals/nord_modal.html: The main user interface for NordVPN setup.
• web/html/settings/xray/outbounds.html: Added "NordVPN" quick-access button.
• web/html/settings/xray/basics.html: Added NordVPN routing rule configuration.
• web/html/xray.html: Enhanced template processing for dynamic outbound tags.

Localization

• web/translation/translate.en_US.toml
• web/translation/translate.fa_IR.toml
• web/translation/translate.zh_CN.toml

Type of Changes

• New feature

Screenshots

[MHSanaei]

Thanks for your PR
please give me access to edit your PR

[PedroLiu1999]

Thanks for your PR please give me access to edit your PR

Permission granted