feat(P2): 实现质量保障类5项功能(无障碍/视觉回归/通知渠道/漏洞扫描/灾备)

## 新增功能

### 1. 屏幕阅读器兼容性增强（a11y）
- 无障碍工具库：src/shared/lib/a11y.ts
- aria-live Hook：src/shared/hooks/use-aria-live.ts
- a11y 组件：skip-link/visually-hidden/focus-trap/aria-status
- 增强 UI：table.tsx 系统性 ARIA role，dialog.tsx aria-modal
- 审计文档：docs/accessibility/a11y-audit.md（WCAG 2.1 AA 清单）

### 2. 视觉回归测试
- 测试套件：tests/visual/（homepage + 3 个 dashboard）
- 3 视口（desktop/tablet/mobile）× 2 主题（light/dark）
- 动态元素遮罩，避免误报
- playwright.config.ts 新增 visual-chromium 项目
- 文档：docs/testing/visual-regression.md

### 3. 短信/微信推送渠道集成
- 新模块：src/modules/notifications/
- 4 个渠道：SMS（阿里云/腾讯云）、WeChat（公众号）、Email（SMTP）、In-App
- 分发器按用户偏好并行多渠道发送
- 外部 SDK 动态 import，Mock 模式开发可用
- 文档：docs/notifications/channels.md

### 4. 漏洞扫描 CI 集成
- CI security-scan job：npm audit + Snyk + Trivy FS + OWASP ZAP
- 独立工作流 security.yml：每周一深度扫描 + 容器镜像扫描
- 配置：suppressions.json + .trivyignore
- 本地脚本：security-scan.sh/ps1
- 文档：docs/security/scanning.md（SLA 分级）

### 5. 灾备方案
- 脚本：backup-verify/backup-offsite-sync/dr-drill/failover/health-check
- CI 增强：备份后校验+异地同步，每周灾备演练
- 独立工作流 dr-drill.yml：每周一凌晨 4 点自动演练
- 文档：docs/dr/dr-plan.md（RTO 4h/RPO 24h）+ dr-runbook.md（6 故障场景）

## 验证
- npx tsc --noEmit：0 错误
- npm run lint：0 错误 0 警告

src/shared/components/ui/dialog.tsx

@@ -37,6 +37,7 @@ const DialogContent = React.forwardRef<
     <DialogOverlay />
     <DialogPrimitive.Content
       ref={ref}
+      aria-modal="true"
       className={cn(
         "fixed left-[50%] top-[50%] z-50 grid w-full max-w-lg translate-x-[-50%] translate-y-[-50%] gap-6 border bg-background p-6 shadow-xl shadow-black/5 duration-200 data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95 sm:rounded-xl",
         className
@@ -44,9 +45,9 @@ const DialogContent = React.forwardRef<
       {...props}
     >
       {children}
-      <DialogPrimitive.Close className="absolute right-4 top-4 rounded-sm opacity-70 ring-offset-background transition-opacity hover:opacity-100 focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:pointer-events-none data-[state=open]:bg-accent data-[state=open]:text-muted-foreground">
+      <DialogPrimitive.Close aria-label="关闭" className="absolute right-4 top-4 rounded-sm opacity-70 ring-offset-background transition-opacity hover:opacity-100 focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:pointer-events-none data-[state=open]:bg-accent data-[state=open]:text-muted-foreground">
         <X className="h-4 w-4" />
-        <span className="sr-only">Close</span>
+        <span className="sr-only">关闭</span>
       </DialogPrimitive.Close>
     </DialogPrimitive.Content>
   </DialogPortal>

src/shared/components/ui/table.tsx

@@ -5,10 +5,11 @@ import { cn } from "@/shared/lib/utils"
 const Table = React.forwardRef<
   HTMLTableElement,
   React.HTMLAttributes<HTMLTableElement>
->(({ className, ...props }, ref) => (
+>(({ className, role = "table", ...props }, ref) => (
   <div className="relative w-full overflow-auto">
     <table
       ref={ref}
+      role={role}
       className={cn("w-full caption-bottom text-sm", className)}
       {...props}
     />
@@ -19,17 +20,23 @@ Table.displayName = "Table"
 const TableHeader = React.forwardRef<
   HTMLTableSectionElement,
   React.HTMLAttributes<HTMLTableSectionElement>
->(({ className, ...props }, ref) => (
-  <thead ref={ref} className={cn("[&_tr]:border-b", className)} {...props} />
+>(({ className, role = "rowgroup", ...props }, ref) => (
+  <thead
+    ref={ref}
+    role={role}
+    className={cn("[&_tr]:border-b", className)}
+    {...props}
+  />
 ))
 TableHeader.displayName = "TableHeader"
 
 const TableBody = React.forwardRef<
   HTMLTableSectionElement,
   React.HTMLAttributes<HTMLTableSectionElement>
->(({ className, ...props }, ref) => (
+>(({ className, role = "rowgroup", ...props }, ref) => (
   <tbody
     ref={ref}
+    role={role}
     className={cn("[&_tr:last-child]:border-0", className)}
     {...props}
   />
@@ -39,9 +46,10 @@ TableBody.displayName = "TableBody"
 const TableFooter = React.forwardRef<
   HTMLTableSectionElement,
   React.HTMLAttributes<HTMLTableSectionElement>
->(({ className, ...props }, ref) => (
+>(({ className, role = "rowgroup", ...props }, ref) => (
   <tfoot
     ref={ref}
+    role={role}
     className={cn(
       "border-t bg-muted/50 font-medium [&>tr]:last:border-b-0",
       className
@@ -54,9 +62,10 @@ TableFooter.displayName = "TableFooter"
 const TableRow = React.forwardRef<
   HTMLTableRowElement,
   React.HTMLAttributes<HTMLTableRowElement>
->(({ className, ...props }, ref) => (
+>(({ className, role = "row", ...props }, ref) => (
   <tr
     ref={ref}
+    role={role}
     className={cn(
       "border-b transition-colors hover:bg-muted/50 data-[state=selected]:bg-muted",
       className
@@ -69,9 +78,10 @@ TableRow.displayName = "TableRow"
 const TableHead = React.forwardRef<
   HTMLTableCellElement,
   React.ThHTMLAttributes<HTMLTableCellElement>
->(({ className, ...props }, ref) => (
+>(({ className, role = "columnheader", ...props }, ref) => (
   <th
     ref={ref}
+    role={role}
     className={cn(
       "h-10 px-2 text-left align-middle font-medium text-muted-foreground [&:has([role=checkbox])]:pr-0 [&>[role=checkbox]]:translate-y-[2px]",
       className
@@ -84,9 +94,10 @@ TableHead.displayName = "TableHead"
 const TableCell = React.forwardRef<
   HTMLTableCellElement,
   React.TdHTMLAttributes<HTMLTableCellElement>
->(({ className, ...props }, ref) => (
+>(({ className, role = "cell", ...props }, ref) => (
   <td
     ref={ref}
+    role={role}
     className={cn(
       "p-2 align-middle [&:has([role=checkbox])]:pr-0 [&>[role=checkbox]]:translate-y-[2px]",
       className