add theme

themes/butterfly/layout/includes/loading/fullpage-loading.pug

@@ -0,0 +1,42 @@
+#loading-box
+  .loading-left-bg
+  .loading-right-bg
+  .spinner-box
+    .configure-border-1
+      .configure-core
+    .configure-border-2
+      .configure-core
+    .loading-word= _p('loading')
+
+script.
+  (()=>{
+    const $loadingBox = document.getElementById('loading-box')
+    const $body = document.body
+    const preloader = {
+      endLoading: () => {
+        if ($loadingBox.classList.contains('loaded')) return
+        $body.style.overflow = ''
+        $loadingBox.classList.add('loaded')
+      },
+      initLoading: () => {
+        $body.style.overflow = 'hidden'
+        $loadingBox.classList.remove('loaded')
+      }
+    }
+
+    preloader.initLoading()
+
+    if (document.readyState === 'complete') {
+      preloader.endLoading()
+    } else {
+      window.addEventListener('load', preloader.endLoading)
+      document.addEventListener('DOMContentLoaded', preloader.endLoading)
+      // Add timeout protection: force end after 7 seconds
+      setTimeout(preloader.endLoading, 7000)
+    }
+
+    if (!{theme.pjax && theme.pjax.enable}) {
+      btf.addGlobalFn('pjaxSend', preloader.initLoading, 'preloader_init')
+      btf.addGlobalFn('pjaxComplete', preloader.endLoading, 'preloader_end')
+    }
+  })()