feat: Dashboard 刷新频率可配置 — RadioGroup 选择器、动态轮询间隔、手动刷新按钮

- useDashboard hook 改为接受 refetchInterval 动态参数，移除固定 8 秒常量
- Header operations 区域重构为 RadioGroup（手动/10秒/30秒/1分钟/5分钟）+ 倒计时/刷新按钮
- 新增 formatCountdown 工具函数及单元测试
- 新增 .dashboard-refresh-control 和 .dashboard-countdown CSS 类
- 同步更新 DEVELOPMENT.md、README.md、主 specs

tests/web/utils/time.test.ts

@@ -1,6 +1,12 @@
 import { describe, expect, test } from "bun:test";
 
-import { formatDurationUnit, formatRelativeTime, isOlderThan, subtractHours } from "../../../src/web/utils/time";
+import {
+  formatCountdown,
+  formatDurationUnit,
+  formatRelativeTime,
+  isOlderThan,
+  subtractHours,
+} from "../../../src/web/utils/time";
 
 describe("subtractHours", () => {
   test("正常扣减小时", () => {
@@ -54,6 +60,15 @@ describe("formatDurationUnit", () => {
   });
 });
 
+describe("formatCountdown", () => {
+  test("格式化秒级和分钟级倒计时", () => {
+    expect(formatCountdown(0)).toBe("0秒");
+    expect(formatCountdown(59)).toBe("59秒");
+    expect(formatCountdown(60)).toBe("1分0秒");
+    expect(formatCountdown(299)).toBe("4分59秒");
+  });
+});
+
 describe("isOlderThan", () => {
   test("判断时间是否超过阈值", () => {
     const now = new Date("2025-01-01T00:02:00.000Z");