Refactor financial chart implementation

js/charts/ppmt_growth.js

@@ -1,6 +1,6 @@
 import { col } from '../csv.js';
 import {
-  PALETTE, FONT, axisCommon, periodAxis, titleStyle, legendStyle,
+  PALETTE, FONT, axisCommon, periodAxis, titleStyle, standardLegend,
   lineSeries, footnote, watermarks, LAYOUT,
 } from '../theme.js';
 
@@ -53,17 +53,7 @@ export function ppmtGrowthChart(rows, { width, height }) {
       text: '泡泡玛特营收到利润的增速对比（2020H1-2026H1）',
       subtext: '同比增速（%），净利增速显著高于营收增速体现利润弹性',
     },
-    legend: {
-      // 不继承 legendStyle，让 ECharts 按系列自动生成「短线+空心圆」图例
-      top: LAYOUT.legendTop,
-      itemGap: 34,
-      textStyle: {
-        color: PALETTE.ink,
-        fontSize: 14,
-        fontFamily: FONT,
-      },
-      data: ['非GAAP归母净利', '毛利润', '营业收入', '营业成本'],
-    },
+    legend: standardLegend(['非GAAP归母净利', '毛利润', '营业收入', '营业成本'], { itemGap: 34 }),
     grid: { left: 84, right: 56, top: LAYOUT.gridTop, bottom: 80 },
     tooltip: {
       trigger: 'axis',