refactor & feat & fix: 重写SVG生成器，优化前端线路绘制与修复样式

重写服务器端SVG生成逻辑，将原铁路线路图生成功能替换为站点间票价矩阵生成。
优化前端换乘路径绘制：新增线路偏移与弯道处理，避免多条线路路径重叠。
修复站点标记的外层圆圈填充颜色，使其正确使用对应线路的配色。

web/ticket-order.js

@@ -63,10 +63,11 @@
       return out;
   };
 
-  const buildTransitPath = (points, radius = 12) => {
+  const buildTransitPath = (points, radius = 12, options = {}) => {
       const src = Array.isArray(points) ? points.filter(Boolean) : [];
       if (src.length === 0) return '';
       if (src.length === 1) return `M ${src[0].x} ${src[0].y}`;
+      const laneOffset = Number(options?.laneOffset) || 0;
 
       const fmt = (n) => {
           const v = Number(n);
@@ -86,6 +87,23 @@
           const code = String(p?.code || '').trim();
           return !!code && stationTransfer && stationTransfer.has(code);
       };
+      const resolveLaneBendX = (from, to) => {
+          if (!laneOffset) return null;
+          const fromTransfer = isTransfer(from);
+          const toTransfer = isTransfer(to);
+          if (!fromTransfer && !toTransfer) return null;
+
+          const minX = Math.min(from.x, to.x);
+          const maxX = Math.max(from.x, to.x);
+          if ((maxX - minX) < 28) return null;
+
+          const anchorX = toTransfer && !fromTransfer
+              ? to.x
+              : (fromTransfer && !toTransfer ? from.x : ((from.x + to.x) / 2));
+          const candidate = Math.max(minX + 12, Math.min(maxX - 12, anchorX + laneOffset));
+          if (Math.abs(candidate - from.x) < 4 || Math.abs(candidate - to.x) < 4) return null;
+          return candidate;
+      };
       const simplify = (arr) => {
           const out = [];
           for (const p of arr) push(out, p);
@@ -121,7 +139,11 @@
 
           const aT = isTransfer(prev);
           const bT = isTransfer(next);
-          if (bT && !aT) {
+          const bendX = resolveLaneBendX(prev, next);
+          if (Number.isFinite(bendX)) {
+              push(orth, { x: bendX, y: prev.y, code: prev?.code || next?.code });
+              push(orth, { x: bendX, y: y2, code: next?.code || prev?.code });
+          } else if (bT && !aT) {
               push(orth, { x: x2, y: prev.y, code: next?.code });
           } else if (aT && !bT) {
               push(orth, { x: prev.x, y: y2, code: prev?.code });
@@ -366,6 +388,10 @@
           };
 
           const labelPlacements = {};
+          const getLaneOffset = (lineIdx) => {
+              const center = (Math.max(totalLines, 1) - 1) / 2;
+              return Math.max(-18, Math.min(18, Math.round((lineIdx - center) * 4)));
+          };
           const placeLabel = (x, y, isStart, name, enName, color) => {
               const key = `${x},${y},${isStart ? 'left' : 'right'}`;
               const count = labelPlacements[key] || 0;
@@ -411,7 +437,7 @@
                       };
                   });
                   
-                  const d = buildTransitPath(pts, 16);
+                  const d = buildTransitPath(pts, 16, { laneOffset: getLaneOffset(li.idx) });
                   svgContent += `<path d="${d}" fill="none" stroke="${li.color}" stroke-width="8" stroke-linecap="round" stroke-linejoin="round" />`;
                   
                   // Add line name labels at ends
@@ -446,8 +472,8 @@
                   markerSvg += `<circle class="node-core" cx="${x}" cy="${y}" r="6.5" fill="#ffffff" stroke="#334155" stroke-width="2.25" />`;
               } else {
                   const color = uniqueColors[0] || '#93a2b7';
-                  markerSvg += `<circle cx="${x}" cy="${y}" r="12.5" fill="#ffffff" stroke="${color}" stroke-width="5" />`;
-                  markerSvg += `<circle class="node-core" cx="${x}" cy="${y}" r="7" fill="#ffffff" stroke="#334155" stroke-width="2.25" />`;
+                  markerSvg += `<circle cx="${x}" cy="${y}" r="12.5" fill="${color}" stroke="${color}" stroke-width="4" />`;
+                  markerSvg += `<circle class="node-core" cx="${x}" cy="${y}" r="7" fill="#ffffff" stroke="${color}" stroke-width="2.25" />`;
               }
 
               const preferTop = isTransfer || (i % 2 === 0 && y >= baseY + 20);