refactor: split project into web and server directories

- Move frontend to web/ directory
- Add server/ directory for backend
- Restructure project for前后端分离架构

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/src/composables/useAnimationProgress.js

@@ -0,0 +1,37 @@
+import { onBeforeUnmount, onMounted, ref, watch } from 'vue'
+
+export function useAnimationProgress(deps = [], duration = 1100) {
+  const progress = ref(0)
+  let frameId = 0
+
+  const easeOutCubic = (value) => 1 - Math.pow(1 - value, 3)
+
+  function start() {
+    cancelAnimationFrame(frameId)
+
+    if (window.matchMedia?.('(prefers-reduced-motion: reduce)').matches) {
+      progress.value = 1
+      return
+    }
+
+    const startedAt = performance.now()
+    progress.value = 0
+
+    function tick(now) {
+      const elapsed = Math.min((now - startedAt) / duration, 1)
+      progress.value = easeOutCubic(elapsed)
+      if (elapsed < 1) frameId = requestAnimationFrame(tick)
+    }
+
+    frameId = requestAnimationFrame(tick)
+  }
+
+  onMounted(start)
+  onBeforeUnmount(() => cancelAnimationFrame(frameId))
+
+  if (deps.length) {
+    watch(deps, start)
+  }
+
+  return progress
+}