Restyle the web UI as a dark trading terminal

- Single palette (web/src/styles/palette.ts) taken from the Stitch
  design, exposed as ap-* UnoCSS colors and --ap-* CSS variables and
  used for Element Plus dark theme overrides, KLineChart and the news
  iframe; zero radius, JetBrains Mono / Space Grotesk bundled locally
- New sidebar and header layout; trading page, plan card and analysis
  drawer follow the design; other pages use the same panels
- Status API reports today's closed trades, wins and net PnL, shown as
  today's PnL and win rate on the trading page

web/src/utils/text.ts

@@ -4,6 +4,12 @@ export function formatTime(value: string | null | undefined, pattern = "MM-DD HH
   return value ? dayjs(value).format(pattern) : "-"
 }
 
+/** 两个时间点之间的耗时，如「1m 52s」 */
+export function formatDuration(from: string, to: string) {
+  const seconds = Math.round((new Date(to).getTime() - new Date(from).getTime()) / 1000)
+  return seconds >= 60 ? `${Math.floor(seconds / 60)}m ${seconds % 60}s` : `${seconds}s`
+}
+
 /** HTML 转纯文本行；DOMParser 解析的文档不会执行脚本 */
 export function htmlToLines(html: string): string[] {
   const marked = html.replace(/<br\s*\/?>|<\/(?:p|div|li|h\d)>/gi, "\n")