feat: Sentiment desk — gauge threshold alerts (Option B)

Each macro gauge selected in the Sentiment desk can now be independently
configured with three alert criteria:
- Seuil bas (≤): alert when value crosses below
- Seuil haut (≥): alert when value crosses above
- Variation % (Δ%): alert when N-day % change exceeds threshold

Frontend: GaugeThresholdConfig component — one row per selected gauge,
compact grid layout with enable toggle + 3 numeric inputs.
Stored in config.gauge_thresholds[gauge_id].

Backend: _check_sentiment() extended — after CBOE signals, reads
macro_gauge_snapshots history, checks each enabled gauge threshold,
emits sentiment market_events with options_note for each breach.
Gauge → affected_assets mapping covers all 32 gauge keys.

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

frontend/src/pages/AIDesks.tsx

@@ -455,6 +455,89 @@ function FundamentalConfig({
 }
 
 
+function GaugeThresholdConfig({
+  selectedGauges,
+  config,
+  onChange,
+}: {
+  selectedGauges: string[]
+  config: Record<string, any>
+  onChange: (c: Record<string, any>) => void
+}) {
+  if (!selectedGauges.length) return null
+
+  const thresholds: Record<string, any> = config.gauge_thresholds ?? {}
+
+  const update = (gaugeId: string, field: string, val: any) => {
+    const current = thresholds[gaugeId] ?? { enabled: false }
+    onChange({
+      ...config,
+      gauge_thresholds: { ...thresholds, [gaugeId]: { ...current, [field]: val } },
+    })
+  }
+
+  const getGauge = (id: string) => MACRO_GAUGE_LIST.find(g => g.id === id)
+
+  return (
+    <div className="space-y-1.5">
+      <div className="text-xs text-slate-500 mb-2 flex items-center gap-2">
+        <span>Alertes par compteur macro sélectionné</span>
+        <span className="text-slate-700">— laisser vide pour désactiver le critère</span>
+      </div>
+      <div className="grid grid-cols-[auto_1fr_auto_auto_auto] gap-x-3 gap-y-1 items-center text-[10px] text-slate-600 px-1 mb-1">
+        <span />
+        <span>Compteur</span>
+        <span className="text-center w-20">≤ Seuil bas</span>
+        <span className="text-center w-20">≥ Seuil haut</span>
+        <span className="text-center w-16">Δ% alerte</span>
+      </div>
+      {selectedGauges.map(gaugeId => {
+        const gauge   = getGauge(gaugeId)
+        const cfg_g   = thresholds[gaugeId] ?? { enabled: false }
+        const enabled = cfg_g.enabled ?? false
+        return (
+          <div key={gaugeId} className={clsx(
+            'grid grid-cols-[auto_1fr_auto_auto_auto] gap-x-3 items-center px-3 py-2 rounded-lg border transition-colors',
+            enabled ? 'border-rose-700/40 bg-rose-900/10' : 'border-slate-700/30 bg-dark-800/60',
+          )}>
+            <button onClick={() => update(gaugeId, 'enabled', !enabled)} className="shrink-0">
+              {enabled
+                ? <ToggleRight className="w-5 h-5 text-rose-400" />
+                : <ToggleLeft  className="w-5 h-5 text-slate-600" />}
+            </button>
+            <span className={clsx('text-sm', enabled ? 'text-white' : 'text-slate-500')}>
+              {gauge?.label ?? gaugeId}
+              <span className="ml-1.5 text-[10px] text-slate-600">{gauge?.bloc}</span>
+            </span>
+            <input
+              type="number" step="any" placeholder="—"
+              disabled={!enabled}
+              value={cfg_g.low_threshold ?? ''}
+              onChange={e => update(gaugeId, 'low_threshold', e.target.value === '' ? null : parseFloat(e.target.value))}
+              className="w-20 bg-dark-900 border border-slate-700/40 rounded px-2 py-1 text-xs text-white placeholder-slate-700 disabled:opacity-30"
+            />
+            <input
+              type="number" step="any" placeholder="—"
+              disabled={!enabled}
+              value={cfg_g.high_threshold ?? ''}
+              onChange={e => update(gaugeId, 'high_threshold', e.target.value === '' ? null : parseFloat(e.target.value))}
+              className="w-20 bg-dark-900 border border-slate-700/40 rounded px-2 py-1 text-xs text-white placeholder-slate-700 disabled:opacity-30"
+            />
+            <input
+              type="number" step="any" placeholder="—"
+              disabled={!enabled}
+              value={cfg_g.change_pct_threshold ?? ''}
+              onChange={e => update(gaugeId, 'change_pct_threshold', e.target.value === '' ? null : parseFloat(e.target.value))}
+              className="w-16 bg-dark-900 border border-slate-700/40 rounded px-2 py-1 text-xs text-white placeholder-slate-700 disabled:opacity-30"
+            />
+          </div>
+        )
+      })}
+    </div>
+  )
+}
+
+
 function ReportConfig({
   config,
   onChange,
@@ -644,6 +727,18 @@ function DeskEditor({
         })()}
       </div>
 
+      {/* Gauge threshold alerts — Sentiment only */}
+      {d.type === 'sentiment' && d.instruments.length > 0 && (
+        <div>
+          <div className="text-xs text-slate-400 mb-2">Configuration des alertes par compteur</div>
+          <GaugeThresholdConfig
+            selectedGauges={d.instruments}
+            config={d.config}
+            onChange={c => set('config', c)}
+          />
+        </div>
+      )}
+
       {/* Actions */}
       <div className="flex items-center justify-between pt-2 border-t border-slate-700/30">
         <button