feat(escalations): mount time-to-first-action stat-card on /escalations

Surfaces the new GET /analytics/flowpilot/escalations endpoint as a card
above the EscalationQueue list. Closes the loop from yesterday's metric
endpoint commit — seniors and owners see the wedge stat the moment they
open the queue, which is the daily-reps version of the GTM ROI story.

Pieces:
- EscalationMetrics TS interface mirroring the backend Pydantic model
  (incl. metric_definition disclaimer field)
- flowpilotAnalyticsApi.getEscalationMetrics(period) client method
- EscalationMetricCard component:
    * loading skeleton, error state, zero-data empty state
    * avg + median + n_with_action/n_claimed conversion rate
    * humanized seconds → "Ns" / "N.N min" formatting
    * inline disclaimer reminding callers this is in-product time-to-
      first-action only, NOT the savings claim — pair with manual
      baseline (per /codex review's two-metric correction)
- Wired into EscalationQueuePage above EscalationQueue

DS-aligned: card-flat, accent-dim usage held to interactive elements,
text-muted-foreground for secondary copy, font-heading on the headline
number, explicit transition properties (no `transition: all`). Respects
prefers-reduced-motion implicitly (only animation is the loading pulse,
which Tailwind's animate-pulse already gates).

tsc -b clean. No new tests in this commit — component is a thin
state-machine over an axios call; integration coverage comes from the
existing backend tests + the e2e Playwright work in the plan.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/api/flowpilotAnalytics.ts

@@ -1,5 +1,12 @@
 import apiClient from './client'
-import type { FlowPilotDashboard, KnowledgeGapReport, CoverageResponse, FlowQualityResponse, EnhancedPsaMetrics } from '@/types/flowpilot-analytics'
+import type {
+  FlowPilotDashboard,
+  KnowledgeGapReport,
+  CoverageResponse,
+  FlowQualityResponse,
+  EnhancedPsaMetrics,
+  EscalationMetrics,
+} from '@/types/flowpilot-analytics'
 
 export const flowpilotAnalyticsApi = {
   async getDashboard(period: string = '30d'): Promise<FlowPilotDashboard> {
@@ -36,6 +43,13 @@ export const flowpilotAnalyticsApi = {
     })
     return response.data
   },
+
+  async getEscalationMetrics(period: string = '30d'): Promise<EscalationMetrics> {
+    const response = await apiClient.get<EscalationMetrics>('/analytics/flowpilot/escalations', {
+      params: { period },
+    })
+    return response.data
+  },
 }
 
 export default flowpilotAnalyticsApi