Add highdpi text/control setting, detect dark

Detects for system dark mode on startup since many users don't know about dark mode. Won't override any existing setting, just detects if no cfg exists `new()`.

Text/control dpi scaling is opt-in for high dpi users, reduces font blurriness.
https://github.com/kwsch/PKHeX/discussions/4458#discussioncomment-12362513
The hover-preview was rewritten in the past year to directly paint instead of updating many controls, so it works fine with `DpiUnawareGdiScaled`. I've not checked extensively to see if anything becomes broken, so user beware 💫

PKHeX.WinForms/Program.cs

@@ -39,6 +39,8 @@ static Program()
 
         if (Settings.Startup.DarkMode)
             Application.SetColorMode(SystemColorMode.Dark);
+        if (Settings.Startup.HighDpiText)
+            Application.SetHighDpiMode(HighDpiMode.DpiUnawareGdiScaled);
     }
 
     [STAThread]

PKHeX.WinForms/Settings/StartupSettings.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Windows.Forms;
 using PKHeX.Core;
 
 namespace PKHeX.WinForms;
@@ -12,11 +13,14 @@ public sealed class StartupSettings : IStartupSettings
     public string Version { get; set; } = string.Empty;
 
     [LocalizedDescription("Use the Dark color mode for the application on startup.")]
-    public bool DarkMode { get; set; }
+    public bool DarkMode { get; set; } = Application.SystemColorMode == SystemColorMode.Dark; // auto-detect for new settings, json load preserves any choice.
 
     [LocalizedDescription("Force HaX mode on Program Launch")]
     public bool ForceHaXOnLaunch { get; set; }
 
+    [LocalizedDescription("Toggles a higher Dpi rendering mode for the application on startup.")]
+    public bool HighDpiText { get; set; } // opt-in
+
     [LocalizedDescription("Skips displaying the splash screen on Program Launch.")]
     public bool SkipSplashScreen { get; set; }