Add configurable BasePath for subfolder hosting and update frontend base handling

Program.cs

@@ -38,6 +38,12 @@ builder.Services.ConfigureHttpJsonOptions(options =>
 
 var app = builder.Build();
 
+var basePath = builder.Configuration["BasePath"];
+if (!string.IsNullOrWhiteSpace(basePath))
+{
+    app.UsePathBase(basePath);
+}
+
 app.UseGlobalExceptionLogging();
 
 // Ensure database and migrations are applied on startup