feat: Market Events — catégories, cleanup sidebar, rename

- Supprime Timeline & ImpactMonitor du routing (redirects /impact + /timeline → /market-events)
- Renomme 'Instrument Snap.' → 'Instrument Analysis' dans la sidebar
- Onglet 'Catégories & Defaults' dans Market Events: CRUD complet (créer/éditer/supprimer)
  chaque catégorie a une table d'impacts par défaut (instrument, sensibilité, direction, notes)
- impact_service: meilleur matching catégorie (sub_type fuzzy + type fallback)
- DB: delete_event_category() + DELETE /api/impact/categories/{name}

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

frontend/src/App.tsx

@@ -23,10 +23,8 @@ import VaRAnalysis from './pages/VaRAnalysis'
 import PositionHistory from './pages/PositionHistory'
 import InstitutionalReports from './pages/InstitutionalReports'
 import SpecialistDesks from './pages/SpecialistDesks'
-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 MarketEvents from './pages/MarketEvents'
 import { Navigate } from 'react-router-dom'
@@ -68,11 +66,12 @@ export default function App() {
             <Route path="/logs" element={<SystemLogs />} />
             <Route path="/institutional" element={<InstitutionalReports />} />
             <Route path="/specialist-desks" element={<SpecialistDesks />} />
-            <Route path="/timeline" element={<Timeline />} />
             <Route path="/snapshot" element={<ExternalSnapshot />} />
             <Route path="/instruments" element={<Navigate to="/instruments/SPY" replace />} />
             <Route path="/instruments/:id" element={<InstrumentDashboard />} />
-            <Route path="/impact" element={<ImpactMonitor />} />
+            {/* Legacy redirects */}
+            <Route path="/impact" element={<Navigate to="/market-events" replace />} />
+            <Route path="/timeline" element={<Navigate to="/market-events" replace />} />
             <Route path="/market-events" element={<MarketEvents />} />
             <Route path="/cycle-actions" element={<CycleActions />} />
           </Routes>