Add multi-factor conviction gate to activation

Make "qualified" mean an edge candidate, not just R:R + confidence.
The gate now also requires (all admin-configurable, defaults on):
- high conviction: recommended_action LONG_HIGH / SHORT_HIGH only
- clean read: risk_level Low (no contradicting signals)
- probable primary target: best target probability >= min (default 60)

- Shared predicate: app/services/qualification.py +
  frontend/src/lib/qualification.ts (mirrored)
- Activation config extended (min_target_probability,
  require_high_conviction, exclude_conflicts) with bool-aware
  get/update + validation
- /trades/performance switched to ?qualified_only=true, applying
  the full gate server-side; confidence breakdown stays unfiltered
- Dashboard "Qualified", Signals "Qualified only" toggle, and
  Track Record all use the one gate; Admin gains the new controls

Sentiment provider runtime config (prior change) included.

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

frontend/src/pages/AdminPage.tsx

@@ -1,5 +1,6 @@
 import { useState } from 'react';
 import { ActivationSettings } from '../components/admin/ActivationSettings';
+import { SentimentProviderSettings } from '../components/admin/SentimentProviderSettings';
 import { DataCleanup } from '../components/admin/DataCleanup';
 import { JobControls } from '../components/admin/JobControls';
 import { PipelineReadinessPanel } from '../components/admin/PipelineReadinessPanel';
@@ -30,6 +31,7 @@ export default function AdminPage() {
         {activeTab === 'Settings' && (
           <div className="space-y-4">
             <ActivationSettings />
+            <SentimentProviderSettings />
             <TickerUniverseBootstrap />
             <RecommendationSettings />
             <SettingsForm />