feat: KPIs con totales absolutos, backfill ads y ventas en cruce canal

Comparativas WoW/MoM/YoY muestran prev/Δ además del %; sync ads admite
histórico desde 2025; tabla ads↔CRM añade cierres, ventas y ROAS.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/middleware.ts

@@ -52,11 +52,12 @@ export async function middleware(req: NextRequest) {
   const url = req.nextUrl.clone();
   const path = url.pathname;
 
-  // Public: login, attribution script, health, inbound webhooks (CRM)
+  // Public: login, attribution script, health, inbound webhooks (CRM), cron (Bearer CRON_SECRET)
   const isPublic =
     path === '/login' ||
     path === '/api/health' ||
     path.startsWith('/api/webhooks/') ||
+    path.startsWith('/api/cron/') ||
     path === '/_4v_attr.js' ||
     path.startsWith('/_next') ||
     path === '/favicon.ico' ||