fix(web): Y/n 按鈕 CSRF Token 缺失修復 (Phase 22 P0)

修復問題:
- 按鈕點擊無反應：CSRF token 載入中或失敗時，buttons 現在會被 disabled
- 增加 toast.error() 提示：當 token 缺失時，顯示「安全驗證失敗」提示

變更:
- handleSign: 新增 toast.error() 當 csrfToken 為 null
- confirmReject: 新增 toast.error() 當 csrfToken 為 null
- ApprovalCard isLoading: 擴展為 signing || csrfLoading || csrfError

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/src/components/approval/live-approval-panel.tsx

@@ -28,6 +28,7 @@ import {
   GlassCardTitle,
   GlassCardContent,
 } from '@/components/ui/glass-card'
+import { toast } from '@/components/ui/toast'
 import { StatusOrb } from '@/components/ui/status-orb'
 import { cn } from '@/lib/utils'
 import { ShieldX, Lock, AlertTriangle } from 'lucide-react'
@@ -154,6 +155,7 @@ export function LiveApprovalPanel({
     // Phase 20: CSRF 保護 - 必須有 Token 才能簽核
     if (!csrfToken) {
       console.error('[HITL] CSRF token not available, cannot sign')
+      toast.error('安全驗證失敗，請重新整理頁面後再試')
       return
     }
 
@@ -209,6 +211,7 @@ export function LiveApprovalPanel({
     // Phase 20: CSRF 保護 - 必須有 Token 才能拒絕
     if (!csrfToken) {
       console.error('[HITL] CSRF token not available, cannot reject')
+      toast.error('安全驗證失敗，請重新整理頁面後再試')
       return
     }
 
@@ -334,7 +337,7 @@ export function LiveApprovalPanel({
               onApprove={() => handleSign(approval.id, approval.riskLevel)}
               onReject={() => handleReject(approval.id)}
               holdDuration={2000}
-              isLoading={signingStates[approval.id] === 'signing'}
+              isLoading={signingStates[approval.id] === 'signing' || csrfLoading || !!csrfError}
               readOnly={isResolved}
             />