fix(dataProcessor): parse DD/M/YY dates from column C in sell-out CSV

Add support for European day-first date format (e.g. "23/2/26" = 23 Feb 2026)
in the sell-out CSV pipeline so months and years are correctly extracted from
column C of Amazon Sell Out 2023-2025.csv.

- normalizeMonth: detect DD/MM/YY when first part > 12, return "Mon-YY"
- mapRowToRecord: add 'C', 'Date', 'Fecha', 'DATA' to month column aliases
- validateSellOutHeaders: accept date columns as substitute for YEAR + MONTH

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

CLAUDE.md

@@ -12,64 +12,24 @@ npm run preview   # Preview production build
 
 No test or lint scripts are configured. ESLint config exists (`eslint.config.js`) but has no npm script.
 
-## Environment
+## Deployment
 
-Requires Node.js >= 18. Set `GEMINI_API_KEY` in `.env.local` for the AI chat feature (Google Gemini API).
-
-## Project Structure
+Project: `craze-analytix2` under Vercel team `christians-projects-dd62b5fc`.
 
+```bash
+vercel --prod --scope christians-projects-dd62b5fc
 ```
-├── App.tsx                  # Main app component, global state orchestrator
-├── index.tsx                # React entry point
-├── index.html               # HTML template (Tailwind CDN loaded here)
-├── types.ts                 # All TypeScript interfaces
-├── vite.config.ts           # Vite config (port 3000, proxy routes, path alias)
-├── vercel.json              # Vercel deployment config (API rewrites, SPA routing)
-├── firebase.json            # Firebase hosting config (alternative deployment)
-├── api/                     # Vercel serverless functions
-│   ├── ask-gemini.ts        # Gemini AI chat proxy
-│   ├── fetch-data.ts        # Sales CSV from Dropbox
-│   ├── fetch-ads.ts         # Ads Excel from Dropbox
-│   ├── fetch-traffic.ts     # Traffic data
-│   ├── fetch-stock.ts       # Item availability
-│   ├── fetch-paneu-stock.ts # PAN-EU vendor stock
-│   ├── fetch-uk-inventory.ts# UK inventory
-│   ├── fetch-buybox.ts      # Buy Box tracker
-│   ├── fetch-forecast.ts    # Forecast data
-│   └── fetch-vendor-stock.ts
-├── components/              # React components
-│   ├── Dashboard.tsx        # KPI cards, charts, YoY comparisons
-│   ├── DataGrid.tsx         # Pivot table with Excel-style filters (~96KB)
-│   ├── WeeklyGrid.tsx       # Weekly time-series view
-│   ├── TopMovers.tsx        # Growth/decline analysis
-│   ├── AdsPerformance.tsx   # Ad spend, ROAS, ACOS metrics
-│   ├── ForecastView.tsx     # Product forecasts with seasonality
-│   ├── FilterBar.tsx        # Sticky filter controls
-│   ├── AIChat.tsx           # AI assistant sidebar
-│   ├── FileUpload.tsx       # Manual data upload modal
-│   ├── ExcelFilter.tsx      # Advanced column filtering UI
-│   ├── MultiSelectDropdown.tsx # Reusable filter dropdown
-│   ├── StockBadge.tsx       # Stock status indicator
-│   ├── VendorStockBadge.tsx # Vendor stock indicator
-│   ├── BuyBoxWarningBadge.tsx # Buy Box loss warnings
-│   ├── Top50Badge.tsx       # Top 50 product badge
-│   ├── InColumnStockFilter.tsx # In-column stock filter
-│   ├── NumericColumnFilter.tsx # Numeric column filter
-│   ├── CrazeLogo.tsx        # Header branding
-│   ├── ErrorBoundary.tsx    # Error handling wrapper
-│   └── Icons.tsx            # SVG icon library
-├── services/                # Business logic and data layer
-│   ├── dataProcessor.ts     # Core data engine (~2400 lines)
-│   ├── storage.ts           # IndexedDB + localStorage caching
-│   ├── geminiService.ts     # AI context builder + API calls
-│   └── filterHelper.ts      # Filter utilities
-└── public/                  # Static data files
-    ├── fc 26.xlsx           # EU forecast
-    ├── fc UK 26.xlsx        # UK forecast
-    ├── Item Availability.xlsx
-    ├── Buy_Box_tracker.xlsx
-    └── Vendor Stock.xlsx
-```
+
+The `.vercel/project.json` must point to `projectId: prj_TYI5xVvuZ0kPI5Ap8zmX7cqfjsCi` and `orgId: team_5AhzZHthpZINNw9vOrKxOINr`.
+
+## Environment Variables
+
+| Variable | Used in | Purpose |
+|---|---|---|
+| `GEMINI_API_KEY` | `.env.local` | AI chat (Google Gemini) |
+| `SUPABASE_URL` | Vercel env / serverless | Supabase project URL |
+| `SUPABASE_SERVICE_KEY` | `api/experiments.ts`, `api/upload-vendor-data.ts` | Server-side Supabase access |
+| `SUPABASE_ANON_KEY` | `services/supabase.ts` | Client-side Supabase access |
 
 ## Architecture
 
@@ -87,41 +47,59 @@ Dropbox (CSV/Excel files)
 
 Data is cached in IndexedDB via `services/storage.ts`. On load, cached data displays immediately while fresh data fetches in the background.
 
+All data sources are fetched automatically from Dropbox — there is no manual file upload.
+
 ### Key Files
 
-- **App.tsx** — Main orchestrator. Holds all global state (rawData, adsData, trafficData, filters, etc.) and passes data/handlers as props to views.
-- **services/dataProcessor.ts** (~2400 lines) — Core data engine. Handles CSV/Excel parsing, currency normalization (EU `1.234,56` and US `1,234.56` formats), Spanish/English month mapping, filtering (`filterData`, `filterAdsData`), aggregation (`aggregateData`), and pivot table generation (`pivotSalesData`).
-- **types.ts** — All TypeScript interfaces: `SalesRecord`, `AdsRecord`, `TrafficRecord`, `ForecastRecord`, `FilterState`, `AggregatedData`, `PivotRow`, etc.
-- **services/storage.ts** — IndexedDB + localStorage caching with schema versioning.
-- **services/geminiService.ts** — Builds structured context from aggregated data and sends to Gemini API.
+- **App.tsx** — Main orchestrator. Holds all global state and passes data/handlers as props to views. All data fetching (`handleDataFetch`, `handleAdsFetch`, `handleBSRFetch`, etc.) is initiated here.
+- **services/dataProcessor.ts** (~2400 lines) — Core data engine. Handles CSV/Excel parsing, currency normalization (EU `1.234,56` and US `1,234.56` formats), Spanish/English month mapping, filtering (`filterData`, `filterAdsData`, `filterBsrData`), aggregation, and pivot table generation.
+- **types.ts** — All TypeScript interfaces: `SalesRecord`, `AdsRecord`, `TrafficRecord`, `ForecastRecord`, `BSRRecord`, `FilterState`, `AggregatedData`, `PivotRow`, `Experiment`, etc.
+- **services/storage.ts** — IndexedDB + localStorage caching with schema versioning. Increment `SCHEMA_VERSION` when changing cached data shapes.
+- **services/experiments.ts** — CRUD operations for experiments via `/api/experiments` (Supabase-backed). Includes ASIN resolution logic for line-level experiments.
+- **services/experimentAnalysis.ts** — Difference-in-Differences (DiD) statistical analysis engine. Uses ISO week boundaries (Monday start).
 
-### Views (rendered conditionally by `view` state in App.tsx)
+### Views
 
-| View | Component | Purpose |
-|------|-----------|---------|
-| dashboard | Dashboard.tsx | KPI cards, charts, YoY comparisons |
-| table | DataGrid.tsx | Pivot table with Excel-style column filters |
-| weekly | WeeklyGrid.tsx | Weekly time-series breakdown |
-| movers | TopMovers.tsx | Top growth/decline products |
-| ads | AdsPerformance.tsx | Ad spend, ROAS, ACOS metrics |
-| forecast | ForecastView.tsx | Product forecasts with velocity mapping |
+| View key | Component | Purpose |
+|----------|-----------|---------|
+| `dashboard` | Dashboard.tsx | KPI cards, charts, YoY comparisons |
+| `table` | DataGrid.tsx | Pivot table with Excel-style column filters |
+| `weekly` | WeeklyGrid.tsx | Weekly time-series breakdown |
+| `movers` | TopMovers.tsx | Top growth/decline products |
+| `ads` | AdsPerformance.tsx | Ad spend, ROAS, ACOS metrics |
+| `forecast` | ForecastView.tsx | Product forecasts with velocity mapping |
+| `vendor` | VendorDataView.tsx | BSR trends, ratings per market. Shows product card (SKU/ASIN/title/BuyBox) when a single ASIN is filtered |
+| `experiments` | ExperimentsView.tsx | A/B experiment tracking with DiD analysis and Bayesian verdicts |
 
 ### API Routes (`/api/`)
 
-All serverless functions fetch data from Dropbox (direct download URLs with `dl=1`). Each returns the raw file content for client-side processing:
-- `fetch-data.ts` (sales CSV), `fetch-ads.ts` (ads Excel), `fetch-traffic.ts`, `fetch-stock.ts`, `fetch-paneu-stock.ts`, `fetch-uk-inventory.ts`, `fetch-buybox.ts`, `fetch-forecast.ts`
-- `ask-gemini.ts` — Proxies chat requests to Google Gemini API
+All fetch routes proxy Dropbox direct-download URLs (`dl=1`) and return raw file content for client-side parsing:
+
+- `fetch-data.ts` — Sales CSV
+- `fetch-ads.ts` — Ads Excel (weekly)
+- `fetch-traffic.ts` — Traffic/Glance Views Excel
+- `fetch-stock.ts` — Item availability
+- `fetch-paneu-stock.ts` — PAN-EU vendor stock
+- `fetch-uk-inventory.ts` — UK inventory
+- `fetch-buybox.ts` — Buy Box tracker Excel
+- `fetch-forecast.ts` — Forecast Excel
+- `fetch-bsr.ts` — BSR/ratings Excel (feeds Vendor tab)
+- `ask-gemini.ts` — Proxies AI chat to Gemini API
+- `experiments.ts` — CRUD for experiments stored in Supabase
+- `upload-vendor-data.ts` — Batch upsert of vendor rows to Supabase
 
 ### Important Constants (in dataProcessor.ts)
 
 - `PAN_EU_COUNTRIES = ['Amazon DE', 'Amazon IT', 'Amazon FR', 'Amazon ES']` — Default country filter when no customer is selected
-- `MONTH_ORDER`, `MONTH_MAP` — Month normalization including Spanish names (Enero→Jan, etc.)
-- `parseCurrency()` — Handles both EU and US number formats
-- Country mapping normalizes various spellings (e.g., "Germany", "Deutschland", "DE", "Alemania" → "Amazon DE")
+- `parseCurrency()` — Handles both EU (`1.234,56`) and US (`1,234.56`) number formats
+- Country mapping normalizes various spellings → `Amazon DE`, `Amazon UK`, etc.
+- `MONTH_MAP` — Normalizes Spanish month names (Enero→Jan, etc.)
 
 ### Filtering Architecture
 
-Filters flow from `FilterBar.tsx` → `App.tsx` state → `filterData()`/`filterAdsData()` in dataProcessor.ts. When no customer filter is selected, ads data defaults to PAN_EU_COUNTRIES only. Sales data and ads data have separate filter functions.
+Filters flow: `FilterBar.tsx` → `App.tsx` state → `filterData()` / `filterAdsData()` / `filterBsrData()` in dataProcessor.ts. When no customer filter is selected, ads data defaults to PAN_EU_COUNTRIES only. Sales and ads data have separate filter functions.
+
+`globalAsinMetadata` (`Map<string, {sku, title, line}>`) is built from `rawData` in App.tsx and passed to views that need product metadata lookups.
 
 ### Path Alias