Refactor theme resource dictionary retrieval logic

Replaced separate calls to GetResourceDictionary and UpdateResourceDictionary with a single GetThemeResourceDictionary call in Theme.cs. Updated blur enablement check to use the new dictionary variable, simplifying theme resource management.

Author: Jack251970

Flow.Launcher.Core/Resource/Theme.cs

@@ -418,11 +418,6 @@ public bool ChangeTheme(string theme = null)
                 if (string.IsNullOrEmpty(path))
                     throw new DirectoryNotFoundException($"Theme path can't be found <{path}>");
 
-                // Retrieve theme resource – always use the resource with font settings applied.
-                var resourceDict = GetResourceDictionary(theme);
-
-                UpdateResourceDictionary(resourceDict);
-
                 _settings.Theme = theme;
 
                 // Always allow re-loading default theme, in case of failure of switching to a new theme from default theme
@@ -432,7 +427,8 @@ public bool ChangeTheme(string theme = null)
                 }
 
                 // Check if blur is enabled
-                BlurEnabled = Win32Helper.IsBackdropSupported() && IsThemeBlurEnabled(resourceDict);
+                var dict = GetThemeResourceDictionary(theme);
+                BlurEnabled = Win32Helper.IsBackdropSupported() && IsThemeBlurEnabled(dict);
 
                 // Apply blur and drop shadow effect so that we do not need to call it again
                 _ = RefreshFrameAsync();