Removes the repository-level NoWarn suppression from Directory.Build.props and addresses the warnings that surface on top of the .NET 10 migration in #9179, keeping Debug, Release, and cross-platform publishes warning-free without suppressing warnings globally.
Changes:
- Removes <NoWarn>CA1031;CS1591;NU1507;CA1416;IDE0058;IDE0053;IDE0200</NoWarn> from Directory.Build.props.
- Annotates Windows-only APIs with [SupportedOSPlatform] and [SupportedOSPlatformGuard] so CA1416 accepts that the Windows surface is gated behind Utils.IsWindows() / Utils.IsNonWindows().
- Splits Utils.SetUnixFileMode into a cross-platform wrapper and a private [UnsupportedOSPlatform("windows")] implementation so File.SetUnixFileMode never reaches the analyzer on Windows builds.
- Adds a parameterless constructor to MessageBoxDialog so Avalonia's runtime XAML loader (AVLN3001) can instantiate the dialog.
- Moves the WPF high-DPI configuration from app.manifest to <ApplicationHighDpiMode>PerMonitorV2</ApplicationHighDpiMode> in v2rayN.csproj, fixing WFO0003.
- Adds global using System.Runtime.Versioning; to ServiceLib and v2rayN.Desktop so the platform attributes are usable project-wide.
Introduces options to specify custom PAC file and system proxy script paths for system proxy settings. Updates configuration models, view models, UI bindings, and logic for Linux/OSX proxy handling and PAC management to use these custom paths if provided. Also adds UI elements and localization for the new settings.
