feat(购票页): 添加动态路线箭头并优化代码格式

新增沿路线循环移动的动态指示箭头，自动适配路线总长度计算动画参数；修复文件开头多余的零宽空格，统一renderRouteOverlay函数内的代码缩进。

web/ticket-order.js

@@ -1,4 +1,4 @@
-(() => {
+(() => {
   const $ = (sel) => document.querySelector(sel);
   const fromEl = $('#from');
   const toEl = $('#to');
@@ -474,10 +474,46 @@
     group.appendChild(glow);
     group.appendChild(main);
 
+    // Dynamic arrows pointing to the destination
+    let totalDist = 0;
+    for (let i = 0; i < points.length - 1; i++) {
+        const dx = points[i+1].x - points[i].x;
+        const dy = points[i+1].y - points[i].y;
+        totalDist += Math.sqrt(dx * dx + dy * dy);
+    }
+
+    const speed = 100; // pixels per second
+    const duration = Math.max(1, totalDist / speed);
+    const numArrows = Math.max(1, Math.floor(duration / 0.7)); // one arrow approx every 0.7s
+    const interval = duration / numArrows;
+
+    for (let i = 0; i < numArrows; i++) {
+        const arrowG = document.createElementNS(ns, 'g');
+        const arrowPath = document.createElementNS(ns, 'path');
+        // Chevron shape
+        arrowPath.setAttribute('d', 'M -6 -5 L 4 0 L -6 5');
+        arrowPath.setAttribute('fill', 'none');
+        arrowPath.setAttribute('stroke', '#854d0e'); // Dark brown/orange to contrast with yellow
+        arrowPath.setAttribute('stroke-width', '2.5');
+        arrowPath.setAttribute('stroke-linecap', 'round');
+        arrowPath.setAttribute('stroke-linejoin', 'round');
+
+        const animateMotion = document.createElementNS(ns, 'animateMotion');
+        animateMotion.setAttribute('dur', `${duration}s`);
+        animateMotion.setAttribute('repeatCount', 'indefinite');
+        animateMotion.setAttribute('path', pathData);
+        animateMotion.setAttribute('rotate', 'auto');
+        animateMotion.setAttribute('begin', `-${i * interval}s`);
+
+        arrowG.appendChild(arrowPath);
+        arrowG.appendChild(animateMotion);
+        group.appendChild(arrowG);
+    }
+
     const firstStation = svgEl.querySelector('.map-station');
     if (firstStation) svgEl.insertBefore(group, firstStation);
     else svgEl.appendChild(group);
-  }
+}
 
   function updateSelectionUI(skipPreview = false) {
       if (!(selection[0] && selection[1])) {