Refactor AutoDropShadow logic for clarity and correctness

Simplified the AutoDropShadow method to avoid redundant operations and improve readability. Now, window corner preference and drop shadow effects are set based on blur and backdrop support, with clear comments explaining each case. Removed convoluted branching for more direct logic.

Author: Jack251970

Flow.Launcher.Core/Resource/Theme.cs

@@ -706,30 +706,27 @@ private void SetBlurForWindow(string theme, BackdropTypes backdropType)
 
         private void AutoDropShadow(bool useDropShadowEffect)
         {
-            SetWindowCornerPreference("Default");
-            RemoveDropShadowEffectFromCurrentTheme();
             if (useDropShadowEffect)
             {
                 if (BlurEnabled && Win32Helper.IsBackdropSupported())
                 {
+                    // For themes with blur enabled, the window border is rendered by the system,
+                    // so we set corner preference to round and remove drop shadow effect to avoid rendering issues.
                     SetWindowCornerPreference("Round");
+                    RemoveDropShadowEffectFromCurrentTheme();
                 }
                 else
                 {
+                    // For themes without blur, we set corner preference to default and add drop shadow effect.
                     SetWindowCornerPreference("Default");
                     AddDropShadowEffectToCurrentTheme();
                 }
             }
             else
             {
-                if (BlurEnabled && Win32Helper.IsBackdropSupported())
-                {
-                    SetWindowCornerPreference("Default");
-                }
-                else
-                {
-                    RemoveDropShadowEffectFromCurrentTheme();
-                }
+                // When drop shadow effect is disabled, we set corner preference to default and remove drop shadow effect.
+                SetWindowCornerPreference("Default");
+                RemoveDropShadowEffectFromCurrentTheme();
             }
         }