fix(*): 邮箱与系统公告 - 合并 PR #417 并修复迁移冲突和提醒关闭逻辑

保留历史数据库迁移谱系与公告按需加载，复用邮件配置快照校验注册域名，补充白名单及公告回归测试。

web/test/announcement-prompt-regressions.test.ts

@@ -0,0 +1,14 @@
+import { expect, test } from "bun:test";
+
+test("announcement prompts preserve lazy loading and dismiss even when read synchronization fails", async () => {
+    const source = await Bun.file(new URL("../src/components/layout/system-announcement-center.tsx", import.meta.url)).text();
+    expect(source).toContain('lazy(() => import("@/components/ui/aceternity/announcement-timeline-modal")');
+    expect(source).toContain("{open ? (");
+    expect(source).toContain("<Suspense fallback={null}>");
+    expect(source).toContain("automaticPrompt={automaticPrompt}");
+    expect(source).toContain('onClose={() => dismissAutomaticPrompt("once")}');
+    expect(source).toContain('onDismissToday={() => dismissAutomaticPrompt("today")}');
+    expect(source).toContain("setDismissedFingerprint(fingerprint)");
+    expect(source).toContain("fingerprint === dismissedFingerprint");
+    expect(source).toContain("`${ANNOUNCEMENT_DISMISS_TODAY_PREFIX}.${userId}`");
+});