fix: bootstrap IV history with 1y realized vol to unblock IV Rank from 50

IV Rank was stuck at 50 for all tickers because the formula returns 50.0
when iv_max == iv_min (not enough historical snapshots). Added:
- bootstrap_iv_history(): downloads 1y of closes per ticker, computes
  30d rolling realized vol (annualized), saves each day to iv_history
- POST /api/options-vol/bootstrap-history endpoint (runs in background)
- OptionsLab: auto-detect when IV Rank needs bootstrapping and show
  an amber banner with one-click "Initialiser historique" button

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

frontend/src/pages/OptionsLab.tsx

@@ -1,6 +1,7 @@
 import { useState } from 'react'
 import { useIvWatchlist, useIvSnapshot, useIvHistory } from '../hooks/useApi'
-import { Activity, TrendingUp, TrendingDown, Minus, RefreshCw, ChevronDown, ChevronUp } from 'lucide-react'
+import { Activity, TrendingUp, TrendingDown, Minus, RefreshCw, ChevronDown, ChevronUp, Database } from 'lucide-react'
+import { api } from '../hooks/useApi'
 import clsx from 'clsx'
 
 // ── Helpers ───────────────────────────────────────────────────────────────────
@@ -249,6 +250,8 @@ function WatchlistRow({ item }: { item: any }) {
 // ── Main page ─────────────────────────────────────────────────────────────────
 export default function OptionsLab() {
   const { data, isLoading, refetch, isFetching } = useIvWatchlist()
+  const [bootstrapping, setBootstrapping] = useState(false)
+  const [bootstrapMsg, setBootstrapMsg] = useState<string | null>(null)
   const items: any[] = data?.items || []
 
   const sellVol = items.filter(i => (i.iv_rank ?? 50) >= 80)
@@ -256,8 +259,44 @@ export default function OptionsLab() {
   const neutral = items.filter(i => i.iv_rank != null && i.iv_rank >= 20 && i.iv_rank < 80)
   const noData  = items.filter(i => i.iv_rank == null)
 
+  const handleBootstrap = async () => {
+    setBootstrapping(true)
+    setBootstrapMsg(null)
+    try {
+      await api.post('/options-vol/bootstrap-history')
+      setBootstrapMsg('Bootstrap lancé (~60s) — actualise dans 1 minute pour voir les IV Rank mis à jour.')
+      setTimeout(() => refetch(), 70_000)
+    } catch {
+      setBootstrapMsg('Erreur lors du bootstrap.')
+    } finally {
+      setBootstrapping(false)
+    }
+  }
+
+  // Show bootstrap banner if most items have no meaningful IV Rank (stuck at 50 or null)
+  const needsBootstrap = items.length > 0 && items.filter(i => i.iv_rank == null || i.iv_rank === 50).length > items.length * 0.6
+
   return (
     <div className="p-6 space-y-5">
+      {needsBootstrap && !bootstrapMsg && (
+        <div className="flex items-center justify-between gap-3 px-4 py-3 rounded border border-amber-700/40 bg-amber-900/10 text-xs text-amber-300">
+          <span>⚠️ Historique IV insuffisant — IV Rank bloqué à 50%. Bootstrappe 1 an de données réalisées pour calibrer le Rank.</span>
+          <button
+            onClick={handleBootstrap}
+            disabled={bootstrapping}
+            className="flex items-center gap-1.5 text-xs bg-amber-700/30 hover:bg-amber-700/50 border border-amber-600/50 text-amber-200 px-3 py-1.5 rounded transition-all whitespace-nowrap disabled:opacity-50"
+          >
+            <Database className={clsx('w-3.5 h-3.5', bootstrapping && 'animate-pulse')} />
+            {bootstrapping ? 'Chargement...' : 'Initialiser historique'}
+          </button>
+        </div>
+      )}
+      {bootstrapMsg && (
+        <div className="px-4 py-3 rounded border border-blue-700/40 bg-blue-900/10 text-xs text-blue-300">
+          ℹ️ {bootstrapMsg}
+        </div>
+      )}
+
       <div className="flex items-center justify-between">
         <div>
           <h1 className="text-xl font-bold text-white flex items-center gap-2">