feat: isolated cycle action — Check New Market Events

Décompose le cycle en 8 actions appelables individuellement.
Action 1 implémentée : scan de 4 sources (news RSS, surprises FRED,
MA crossovers yfinance, rapports institutionnels) → création de
market_events avec déduplication. UI CycleActions page + sidebar link.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -27,6 +27,7 @@ import Timeline from './pages/Timeline'
 import ExternalSnapshot from './pages/ExternalSnapshot'
 import InstrumentDashboard from './pages/InstrumentDashboard'
 import ImpactMonitor from './pages/ImpactMonitor'
+import CycleActions from './pages/CycleActions'
 import { Navigate } from 'react-router-dom'
 import { useCycleWatcher } from './hooks/useApi'
 
@@ -71,6 +72,7 @@ export default function App() {
             <Route path="/instruments" element={<Navigate to="/instruments/SPY" replace />} />
             <Route path="/instruments/:id" element={<InstrumentDashboard />} />
             <Route path="/impact" element={<ImpactMonitor />} />
+            <Route path="/cycle-actions" element={<CycleActions />} />
           </Routes>
         </main>
       </div>