refactor: redesign Session History with tabs + Load More, improve Escalation Queue urgency

Session History:
- Split into AI Sessions / Flow Sessions tabs (AI default)
- Load More pagination (25 per page) instead of 50-item hard cap
- Dynamic problem domain filter from actual session data
- Fix all blue focus rings to ember orange
- Fix badge colors to use design system tokens

Escalation Queue:
- Add wait-time color coding (muted <1h, amber 1-4h, red >4h)
- Sort oldest-first for triage urgency
- Compact right-aligned pickup button
- Widen container, dynamic session count in subtitle
- Fix typos and non-system color tokens

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/EscalationQueuePage.tsx

@@ -1,20 +1,27 @@
+import { useState } from 'react'
 import { AlertTriangle } from 'lucide-react'
 import { EscalationQueue } from '@/components/flowpilot'
 
 export default function EscalationQueuePage() {
+  const [count, setCount] = useState<number | null>(null)
+
   return (
-    <div className="mx-auto max-w-3xl p-6">
+    <div className="mx-auto max-w-4xl p-6">
       <div className="flex items-center gap-3 mb-6">
-        <span className="flex h-8 w-8 items-center justify-center rounded-lg bg-amber-500/10">
-          <AlertTriangle size={16} className="text-amber-400" />
+        <span className="flex h-8 w-8 items-center justify-center rounded-lg bg-warning-dim">
+          <AlertTriangle size={16} className="text-warning" />
         </span>
         <div>
           <h1 className="font-heading text-xl font-bold text-foreground">Escalation Queue</h1>
-          <p className="text-sm text-muted-foreground">Sessions from your team waiting for pickup</p>
+          <p className="text-sm text-muted-foreground">
+            {count !== null && count > 0
+              ? `${count} session${count !== 1 ? 's' : ''} waiting for pickup`
+              : 'Sessions from your team waiting for pickup'}
+          </p>
         </div>
       </div>
 
-      <EscalationQueue />
+      <EscalationQueue onCountChange={setCount} />
     </div>
   )
 }