feat: add Experiment Tracker to Weekly Sales tab

Log weekly actions (SEO, pricing, ads, etc.) per product line and visualize
their impact with a Recharts line chart showing experiment markers. Includes
a collapsible experiments panel with auto-computed delta % (3-week before vs
after comparison) and editable status tracking. Data persisted in localStorage.

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

components/WeeklyGrid.tsx

@@ -10,6 +10,7 @@ import { VendorStockBadge } from './VendorStockBadge';
 import { BuyBoxWarningBadge } from './BuyBoxWarningBadge';
 import { WarehouseIcon, AmazonSmileIcon, CoverageIcon } from './Icons';
 import { ExcelFilter } from './ExcelFilter';
+import ExperimentTracker from './ExperimentTracker';
 
 interface WeeklyGridProps {
     data: CombinedKPIs[];
@@ -664,6 +665,9 @@ const WeeklyGrid: React.FC<WeeklyGridProps & { top50Mode: 'eu' | 'uk' }> = ({
 
     return (
         <div className="flex flex-col gap-3 md:gap-4 animate-fade-in px-1 md:px-0">
+            {/* Experiment Tracker */}
+            <ExperimentTracker rows={rows} weeks={weeks} primaryMetric={primaryMetric} />
+
             {/* Toolbar: Search & Pagination */}
             <div className="flex flex-col lg:flex-row justify-between items-center gap-3 md:gap-4 bg-slate-900 border border-white/10 p-2 md:p-4 rounded-xl shadow-lg">
                 <div className="flex flex-wrap items-center gap-4 w-full lg:w-auto">