feat: 列宽拖拽 + 筛选栏 + 截图导出 + UI优化

- 新增 v-column-resize 指令，11 张表格均支持拖拽调整列宽
- 工作计划/商机跟单/要客拜访新增筛选栏（客户经理 + 状态）
- 汇总栏 chip 可点击筛选，支持重置与计数
- 新增截图导出功能（dom-to-image-more，像素级文字渲染）
- 截图范围从标题开始，自动隐藏操作按钮，5px白边
- 截图时页面闪烁动画反馈
- 全局 CSS 完善（列宽手柄、截图模式、捕获动画）
- 仪表盘 UI 细节优化 + 亮灯表标签调整
- 登录页 UI 改进

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/utils/screenshot.ts

@@ -0,0 +1,72 @@
+/**
+ * useScreenshot — capture a DOM element as PNG and trigger download.
+ *
+ * Uses dom-to-image-more (SVG foreignObject) for pixel-perfect text rendering —
+ * unlike html2canvas, the browser itself paints the text so there's zero offset.
+ *
+ * Usage:
+ *   const { capturing, captureEl } = useScreenshot()
+ *   <div ref="shotRef">...</div>
+ *   <button @click="captureEl(shotRef, 'filename')">截图</button>
+ */
+
+import { ref, nextTick } from 'vue'
+import domtoimage from 'dom-to-image-more'
+
+export function useScreenshot() {
+  const capturing = ref(false)
+
+  async function captureEl(el: HTMLElement | null, filename: string): Promise<boolean> {
+    if (!el || capturing.value) return false
+    capturing.value = true
+    await nextTick()
+
+    el.classList.add('taking-screenshot')
+    document.body.classList.add('body-capturing')
+    await new Promise((r) => setTimeout(r, 80))
+
+    try {
+      const dataUrl = await domtoimage.toPng(el, {
+        bgColor: '#ffffff',
+        width: el.scrollWidth,
+        height: el.scrollHeight,
+        quality: 1,
+        cacheBust: true,
+      })
+
+      // Pad 5px white border around the image
+      const img = await new Promise<HTMLImageElement>((resolve, reject) => {
+        const i = new Image()
+        i.onload = () => resolve(i)
+        i.onerror = reject
+        i.src = dataUrl
+      })
+
+      const PAD = 5
+      const canvas = document.createElement('canvas')
+      canvas.width = img.width + PAD * 2
+      canvas.height = img.height + PAD * 2
+      const ctx = canvas.getContext('2d')!
+      ctx.fillStyle = '#ffffff'
+      ctx.fillRect(0, 0, canvas.width, canvas.height)
+      ctx.drawImage(img, PAD, PAD)
+
+      const link = document.createElement('a')
+      link.download = filename
+      link.href = canvas.toDataURL('image/png')
+      document.body.appendChild(link)
+      link.click()
+      document.body.removeChild(link)
+      return true
+    } catch (e) {
+      console.error('Screenshot failed:', e)
+      return false
+    } finally {
+      el.classList.remove('taking-screenshot')
+      document.body.classList.remove('body-capturing')
+      capturing.value = false
+    }
+  }
+
+  return { capturing, captureEl }
+}