refactor(wel): 重构欢迎页为模块化组件

- 将欢迎页整体结构拆分为多个功能区组件，提高代码可维护性
- 移除原有欢迎横幅、指标卡、图表区、下方区及快捷入口的静态实现
- 引入并注册 SectionKpi、SectionStructure、SectionBusiness 等八个子组件
- 删除冗余样式，更新整体背景和布局样式
- 精简模板内容，仅保留子组件渲染及页脚版权信息
- 移除无用的响应式数据、计算属性及方法
- 包含依赖包 echarts 的新增，支持后续图表功能开发

src/views/wel/components/wel-chart.vue

@@ -0,0 +1,57 @@
+<template>
+  <div ref="chartEl" class="wel-chart" :style="{ height: height }"></div>
+</template>
+
+<script>
+import * as echarts from 'echarts';
+
+export default {
+  name: 'wel-chart',
+  props: {
+    option: { type: Object, required: true },
+    height: { type: String, default: '260px' },
+  },
+  data() {
+    return {
+      chart: null,
+      resizeObserver: null,
+    };
+  },
+  watch: {
+    option: {
+      deep: true,
+      handler() {
+        this.render();
+      },
+    },
+  },
+  mounted() {
+    this.chart = echarts.init(this.$refs.chartEl);
+    this.render();
+    this.resizeObserver = new ResizeObserver(() => {
+      this.chart && this.chart.resize();
+    });
+    this.resizeObserver.observe(this.$refs.chartEl);
+  },
+  activated() {
+    /* keep-alive 恢复时重算尺寸 */
+    this.chart && this.chart.resize();
+  },
+  beforeUnmount() {
+    this.resizeObserver && this.resizeObserver.disconnect();
+    this.chart && this.chart.dispose();
+    this.chart = null;
+  },
+  methods: {
+    render() {
+      this.chart && this.chart.setOption(this.option, true);
+    },
+  },
+};
+</script>
+
+<style lang="scss" scoped>
+.wel-chart {
+  width: 100%;
+}
+</style>