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/components/layout/Sidebar.tsx

@@ -1,7 +1,7 @@
 import { NavLink } from 'react-router-dom'
 import {
   LayoutDashboard, Globe, BarChart2, FlaskConical,
-  History, Calendar, TrendingUp, Zap, DollarSign, Settings, BrainCircuit, Activity, BookOpen, FileBarChart, Brain, ShieldAlert, Microscope, ScrollText, Gauge, GitCompare, Building2, Users, Layers, ScanEye, CandlestickChart, Crosshair, PlayCircle, Radio
+  History, Calendar, TrendingUp, Zap, DollarSign, Settings, BrainCircuit, Activity, BookOpen, FileBarChart, Brain, ShieldAlert, Microscope, ScrollText, Gauge, GitCompare, Building2, Users, ScanEye, CandlestickChart, PlayCircle, Radio
 } from 'lucide-react'
 import { useGeoRiskScore, useAiStatus, usePortfolioSummary } from '../../hooks/useApi'
 import clsx from 'clsx'
@@ -27,12 +27,10 @@ const nav = [
   { to: '/calendar', icon: Calendar, label: 'Calendar' },
   { to: '/institutional', icon: Building2, label: 'Inst. Reports' },
   { to: '/specialist-desks', icon: Users, label: 'Specialist Desks' },
-  { to: '/instruments', icon: CandlestickChart, label: 'Instrument Snap.' },
+  { to: '/instruments', icon: CandlestickChart, label: 'Instrument Analysis' },
   { to: '/market-events', icon: Radio, label: 'Market Events' },
-  { to: '/impact', icon: Crosshair, label: 'Impact Monitor' },
   { to: '/cycle-actions', icon: PlayCircle, label: 'Cycle Actions' },
   { to: '/snapshot', icon: ScanEye, label: 'Snapshot Externe' },
-  { to: '/timeline', icon: Layers, label: 'Timeline' },
   { to: '/logs', icon: ScrollText, label: 'System Logs' },
   { to: '/config', icon: Settings, label: 'Configuration' },
 ]