fix(analytics): update usePrometheusMetrics to use useApi() response format (#4426) (#4494)

- Convert all 6 fetch functions from response.ok/response.json() pattern to
  direct api.get<T>() typed calls — ApiClient already parses JSON and throws
  on HTTP errors, so Response object API was never valid
- Rename destructured useWebSocket option to enableWebSocket to avoid
  shadowing the imported useWebSocket composable
- Fix implicit any in alertmanagerAlerts filter — add PerformanceAlert type

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: mrveiss

autobot-frontend/src/composables/usePrometheusMetrics.ts

@@ -717,7 +717,7 @@ export function useAlerts(pollInterval = 30000) {
   const hasAlerts = computed(() => totalCount.value > 0)
   // Issue #474: Computed for AlertManager-specific alerts
   const alertmanagerAlerts = computed(() =>
-    alerts.value.filter(a => a.source === 'alertmanager')
+    alerts.value.filter((a: PerformanceAlert) => a.source === 'alertmanager')
   )
 
   function startPolling() {