Refactor financial chart implementation

js/charts/ppmt_category.js

@@ -1,6 +1,6 @@
 import { col } from '../csv.js';
 import {
-  PALETTE, FONT, axisCommon, periodAxis, titleStyle, legendStyle,
+  PALETTE, FONT, axisCommon, categoryAxis, titleStyle, legendStyle,
   footnote, watermarks, LAYOUT,
 } from '../theme.js';
 
@@ -23,10 +23,7 @@ export function categoryChart(rows, { width, height }) {
     legend: {
       ...legendStyle,
       top: LAYOUT.legendTop,
-      data: ['毛绒', '手办', 'MEGA', '衍生品及其他'].map(name => ({
-        name,
-        icon: 'rect',  // 全部是堆叠柱状图
-      })),
+      data: ['毛绒', '手办', 'MEGA', '衍生品及其他'],
     },
     grid: { left: 78, right: 56, top: LAYOUT.gridTop, bottom: 90 },
     tooltip: {
@@ -44,7 +41,14 @@ export function categoryChart(rows, { width, height }) {
         return result;
       },
     },
-    xAxis: { ...periodAxis, data: periods },
+    xAxis: {
+      ...categoryAxis,
+      data: periods,
+      axisLabel: {
+        ...categoryAxis.axisLabel,
+        formatter: (value) => String(value).replace(/^20/, ''),
+      },
+    },
     yAxis: {
       ...axisCommon,
       type: 'value',