feat: Stripe Checkout, Zeptomail, pre-alert linking, perfil 3-tab, carga-pesada landing

- payments: real Stripe Checkout Session (redirect flow), confirmBySession, webhook handler
- notifications: Zeptomail REST email, wa.me WhatsApp links, IntegrationsService injection
- auth: changePassword, updateProfile, disableMfa (TOTP-verified) endpoints
- packages: tryLinkPreAlert() auto-links on create (non-blocking)
- integrations: catalog updated (zeptomail, stripe_webhook_secret; removed sendgrid/whatsapp-api)
- web/portal/perfil: 3-tab layout (datos / contraseña / MFA)
- web/portal/pago: Stripe redirect + ?success=1&session_id= callback, cancelled banner
- web/admin/b2b: fix enum values (EN_COTIZACION, ACEPTADO)
- web/carga-pesada: rich marketing landing (FCL/LCL, 7-step process, sectors, INEN callout)
- tests: fix payments.service.spec (IntegrationsService+ConfigService mocks)
- tests: fix notifications.service.spec (IntegrationsService mock, phone in mockUser)
- all 104 tests passing, API + web builds clean

apps/api/package.json

@@ -31,7 +31,8 @@
     "passport": "^0.7.0",
     "passport-jwt": "^4.0.1",
     "reflect-metadata": "^0.2.2",
-    "rxjs": "^7.8.2"
+    "rxjs": "^7.8.2",
+    "stripe": "^22.2.0"
   },
   "devDependencies": {
     "@nestjs/cli": "^11.0.7",