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/pages/AdminPage.tsx

@@ -1,4 +1,5 @@
 import { useState } from 'react';
+import { ActivationSettings } from '../components/admin/ActivationSettings';
 import { DataCleanup } from '../components/admin/DataCleanup';
 import { JobControls } from '../components/admin/JobControls';
 import { PipelineReadinessPanel } from '../components/admin/PipelineReadinessPanel';
@@ -28,6 +29,7 @@ export default function AdminPage() {
         {activeTab === 'Tickers' && <TickerManagement />}
         {activeTab === 'Settings' && (
           <div className="space-y-4">
+            <ActivationSettings />
             <TickerUniverseBootstrap />
             <RecommendationSettings />
             <SettingsForm />