feat: 数据标签颜色默认同系列+可自定义；Y轴最小/最大值手动指定 v1.20.0

- 数据标签颜色：默认自动取系列颜色(柱状/折线色)，也可选自定义颜色手动指定
- Y轴范围：默认自动计算，可手动指定最小/最大值；双Y轴时左/右轴可分别指定
- 主图 + 多图合并 + 服务端API 三处统一；收藏保存/恢复含两项设置
- API 新增参数 labelColorMode/labelColor, yAxisMin/yAxisMax, leftAxisMin/Max, rightAxisMin/Max

server.js

@@ -152,6 +152,13 @@ function applySeriesStyle(seriesItem, type, color, style) {
     }
 }
 
+// Y轴 min/max：空值/非法返回 undefined（ECharts 自动）
+function axisNum(v) {
+    if (v === '' || v === undefined || v === null) return undefined;
+    const n = parseFloat(v);
+    return isNaN(n) ? undefined : n;
+}
+
 function buildChartOption(params) {
     const {
         data,
@@ -178,6 +185,14 @@ function buildChartOption(params) {
         seriesStyles = null,
         leftAxisNameLoc = 'vertical',
         rightAxisNameLoc = 'vertical',
+        labelColorMode = 'auto',
+        labelColor = '#333333',
+        yAxisMin = '',
+        yAxisMax = '',
+        leftAxisMin = '',
+        leftAxisMax = '',
+        rightAxisMin = '',
+        rightAxisMax = '',
         width = 800
     } = params;
 
@@ -315,12 +330,13 @@ function buildChartOption(params) {
         const st = Array.isArray(seriesStyles) ? seriesStyles[idx] : null;
         applySeriesStyle(seriesItem, type, color, st);
 
+        // 数据标签：颜色默认同系列颜色，可手动自定义
         if (showLabel) {
             seriesItem.label = {
                 show: true,
                 position: 'top',
                 fontSize: 11,
-                color: textColor,
+                color: labelColorMode === 'custom' ? labelColor : color,
                 formatter: (p) => {
                     if (p.value >= 10000) return (p.value / 10000).toFixed(1) + 'w';
                     if (p.value >= 1000) return (p.value / 1000).toFixed(1) + 'k';
@@ -470,6 +486,8 @@ function buildChartOption(params) {
             {
                 type: 'value',
                 name: leftAxisName || '左轴',
+                min: axisNum(leftAxisMin),
+                max: axisNum(leftAxisMax),
                 nameLocation: leftAxisNameLoc === 'top' ? 'end' : 'middle',
                 nameRotate: leftAxisNameLoc === 'top' ? 0 : 90,
                 nameGap: leftAxisNameLoc === 'top' ? 12 : 32,
@@ -489,6 +507,8 @@ function buildChartOption(params) {
                 type: 'value',
                 name: rightAxisName || '右轴',
                 position: 'right',
+                min: axisNum(rightAxisMin),
+                max: axisNum(rightAxisMax),
                 nameLocation: rightAxisNameLoc === 'top' ? 'end' : 'middle',
                 nameRotate: rightAxisNameLoc === 'top' ? 0 : 90,
                 nameGap: rightAxisNameLoc === 'top' ? 12 : 32,
@@ -500,6 +520,8 @@ function buildChartOption(params) {
             }
         ] : {
             type: 'value',
+            min: axisNum(yAxisMin),
+            max: axisNum(yAxisMax),
             axisLine: { show: false },
             axisTick: { show: false },
             axisLabel: { color: textColor, fontSize: 11 },
@@ -604,6 +626,14 @@ app.get('/api/chart', (req, res) => {
             seriesStyles: req.query.seriesStyles ? req.query.seriesStyles.split(',') : null,
             leftAxisNameLoc: req.query.leftAxisNameLoc || 'vertical',
             rightAxisNameLoc: req.query.rightAxisNameLoc || 'vertical',
+            labelColorMode: req.query.labelColorMode || 'auto',
+            labelColor: req.query.labelColor || '#333333',
+            yAxisMin: req.query.yAxisMin || '',
+            yAxisMax: req.query.yAxisMax || '',
+            leftAxisMin: req.query.leftAxisMin || '',
+            leftAxisMax: req.query.leftAxisMax || '',
+            rightAxisMin: req.query.rightAxisMin || '',
+            rightAxisMax: req.query.rightAxisMax || '',
             rowsAsSeries: req.query.rowsAsSeries === 'true',
             width: parseInt(req.query.width) || 800,
             height: parseInt(req.query.height) || 500,
@@ -1121,7 +1151,7 @@ app.get('/api/health', (req, res) => {
     res.json({
         status: 'ok',
         service: 'data-chart-tool',
-        version: '1.19.0',
+        version: '1.20.0',
         endpoints: {
             'POST /api/chart': '生成图表图片（JSON body）',
             'GET /api/chart': '生成图表图片（URL 参数）',
@@ -1141,7 +1171,7 @@ app.get('/api/health', (req, res) => {
 app.get('/api/docs', (req, res) => {
     res.json({
         name: '数据可视化图表生成器 API',
-        version: '1.19.0',
+        version: '1.20.0',
         endpoints: [
             {
                 method: 'POST',
@@ -1176,6 +1206,14 @@ app.get('/api/docs', (req, res) => {
                     seriesStyles: { type: 'array', default: null, description: '每系列样式（如 ["solid","dashed"]，柱状支持 solid实体/hollow空心/shadow阴影，折线支持 solid实线/dashed虚线/dotted点线）' },
                     leftAxisNameLoc: { type: 'string', default: 'vertical', options: ['vertical', 'top'], description: '左轴标题显示方式：vertical=竖直显示(默认)，top=轴上部横排' },
                     rightAxisNameLoc: { type: 'string', default: 'vertical', options: ['vertical', 'top'], description: '右轴标题显示方式：vertical=竖直显示(默认)，top=轴上部横排' },
+                    labelColorMode: { type: 'string', default: 'auto', options: ['auto', 'custom'], description: '数据标签颜色：auto=同系列颜色(默认)，custom=手动指定 labelColor' },
+                    labelColor: { type: 'string', default: '#333333', description: '数据标签自定义颜色（labelColorMode=custom 时生效）' },
+                    yAxisMin: { type: 'string', default: '', description: '单Y轴最小值（留空=自动）' },
+                    yAxisMax: { type: 'string', default: '', description: '单Y轴最大值（留空=自动）' },
+                    leftAxisMin: { type: 'string', default: '', description: '双Y轴左轴最小值（留空=自动）' },
+                    leftAxisMax: { type: 'string', default: '', description: '双Y轴左轴最大值（留空=自动）' },
+                    rightAxisMin: { type: 'string', default: '', description: '双Y轴右轴最小值（留空=自动）' },
+                    rightAxisMax: { type: 'string', default: '', description: '双Y轴右轴最大值（留空=自动）' },
                     rowsAsSeries: { type: 'boolean', default: false, description: '数据方向：false=列=系列（第一列是横坐标，每列一个系列）；true=行=系列（第一行是横坐标，每行一个系列）' }
                 },
                 returns: 'image/png',