Add activation thresholds: qualified-signal defaults and views

Admin-configurable thresholds (min R:R, default 2.0; min confidence,
default 70%) defining what counts as an actionable signal:

- Admin Settings: new Activation Thresholds panel
  (GET/PUT /admin/settings/activation)
- GET /trades/activation exposes values to all users with access
- Signals/Setups: filters initialize from activation values
- Track Record: "Qualified signals only" toggle (default on) via
  min_rr/min_confidence params on /trades/performance; the
  confidence breakdown always covers the full population so the
  thresholds can be validated against outcomes
- Dashboard: "Qualified" metric and qualified-first Top Setups
- Outcome evaluator unchanged: every setup is still evaluated

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/api/admin.ts

@@ -1,5 +1,6 @@
 import apiClient from './client';
 import type {
+  ActivationConfig,
   AdminUser,
   PipelineReadiness,
   RecommendationConfig,
@@ -68,6 +69,18 @@ export function updateRecommendationSettings(payload: Partial<RecommendationConf
     .then((r) => r.data);
 }
 
+export function getActivationSettings() {
+  return apiClient
+    .get<ActivationConfig>('admin/settings/activation')
+    .then((r) => r.data);
+}
+
+export function updateActivationSettings(payload: Partial<ActivationConfig>) {
+  return apiClient
+    .put<ActivationConfig>('admin/settings/activation', payload)
+    .then((r) => r.data);
+}
+
 export function getTickerUniverseSetting() {
   return apiClient
     .get<TickerUniverseSetting>('admin/settings/ticker-universe')