fix: Register IThemeManager service to fix DI error

Add AddAutoComplete() call to register core AutoComplete services
including IThemeManager, which is required by the AutoComplete component.

Author: mashrulhaque

samples/AutoComplete.Playground/Program.cs

@@ -1,4 +1,5 @@
 using AutoComplete.Playground.Components;
+using EasyAppDev.Blazor.AutoComplete.Extensions;
 using Microsoft.Extensions.AI;
 using Microsoft.SemanticKernel;
 
@@ -17,6 +18,9 @@
 builder.Services.AddRazorComponents()
     .AddInteractiveServerComponents();
 
+// Register AutoComplete core services (IThemeManager, etc.)
+builder.Services.AddAutoComplete();
+
 // Configure OpenAI for semantic search using the simplified extension method
 builder.Services.AddAutoCompleteSemanticSearch(builder.Configuration);