feat: add Supabase vendor data integration (BSR, ratings, buy box)

- Create vendor_daily_data table schema and Supabase client service
- Add upload API route for Vendor Central CSV parsing and upsert
- Add VendorDataView with BSR trend, ratings, and buy box charts
- Integrate new Vendor tab into app navigation (desktop + mobile)
- Add vendor CSV upload card to FileUpload modal

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

services/supabase.ts

@@ -0,0 +1,114 @@
+
+import { createClient } from '@supabase/supabase-js';
+
+const supabaseUrl = process.env.SUPABASE_URL || '';
+const supabaseAnonKey = process.env.SUPABASE_ANON_KEY || '';
+
+export const supabase = createClient(supabaseUrl, supabaseAnonKey);
+
+export interface VendorDailyRow {
+  id?: number;
+  date: string;
+  market: string;
+  asin: string;
+  product_title: string | null;
+  tags: string | null;
+  bsr_top_rank: number | null;
+  bsr_top_category: string | null;
+  bsr_detail_rank: number | null;
+  bsr_detail_category: string | null;
+  avg_rating: number | null;
+  num_reviews: number | null;
+  buybox_owner: string | null;
+  buybox_price: number | null;
+  amazon_has_buybox: boolean | null;
+  glance_views: number | null;
+}
+
+export interface VendorFilters {
+  markets?: string[];
+  tags?: string[];
+  asins?: string[];
+  dateFrom?: string;
+  dateTo?: string;
+}
+
+export const fetchVendorData = async (filters: VendorFilters): Promise<VendorDailyRow[]> => {
+  const allRows: VendorDailyRow[] = [];
+  let offset = 0;
+  const pageSize = 1000;
+  let hasMore = true;
+
+  while (hasMore) {
+    let query = supabase
+      .from('vendor_daily_data')
+      .select('*')
+      .order('date', { ascending: true })
+      .range(offset, offset + pageSize - 1);
+
+    if (filters.markets?.length) {
+      query = query.in('market', filters.markets);
+    }
+    if (filters.tags?.length) {
+      query = query.in('tags', filters.tags);
+    }
+    if (filters.asins?.length) {
+      query = query.in('asin', filters.asins);
+    }
+    if (filters.dateFrom) {
+      query = query.gte('date', filters.dateFrom);
+    }
+    if (filters.dateTo) {
+      query = query.lte('date', filters.dateTo);
+    }
+
+    const { data, error } = await query;
+    if (error) throw error;
+    if (data) {
+      allRows.push(...data);
+      hasMore = data.length === pageSize;
+      offset += pageSize;
+    } else {
+      hasMore = false;
+    }
+  }
+
+  return allRows;
+};
+
+export const fetchVendorFilterOptions = async (): Promise<{
+  markets: string[];
+  tags: string[];
+  dateRange: { min: string; max: string } | null;
+}> => {
+  const { data: marketData } = await supabase
+    .from('vendor_daily_data')
+    .select('market');
+
+  const { data: tagData } = await supabase
+    .from('vendor_daily_data')
+    .select('tags');
+
+  const { data: dateMin } = await supabase
+    .from('vendor_daily_data')
+    .select('date')
+    .order('date', { ascending: true })
+    .limit(1);
+
+  const { data: dateMax } = await supabase
+    .from('vendor_daily_data')
+    .select('date')
+    .order('date', { ascending: false })
+    .limit(1);
+
+  const markets = [...new Set((marketData || []).map(r => r.market))].sort();
+  const tags = [...new Set((tagData || []).map(r => r.tags).filter(Boolean))].sort();
+
+  return {
+    markets,
+    tags,
+    dateRange: dateMin?.[0] && dateMax?.[0]
+      ? { min: dateMin[0].date, max: dateMax[0].date }
+      : null,
+  };
+};