feat(notificaciones): mass email notifications over SES

Replaces the four legacy PHP scripts under email.notifications/send*.php
with a single NestJS module. Four jobs (outstanding payments, payment
confirmations, account-status alerts with day-of-week gates, trust
payment confirmations) share one MailService modelled on StorageService:
env-driven SES client, null fallback in dev with console logging, refuses
to send in production when unconfigured.

Schema adds email_notification_log (every attempt, sent/failed/skipped)
and account_status_history (one row per threshold hit, Job 3). Enums
encode the legacy wire shape so external log scrapers keep parsing
notificationType keys verbatim.

Web adds /notificaciones with four trigger cards, a flags panel, and a
paginated log browser. New notification:send ability gates all four
endpoints at MANAGER, matching the renewal:send trust tier.

apps/web/src/components/AppShell.tsx

@@ -78,6 +78,11 @@ const NAV: NavEntry[] = [
         label: "Cuentas de chequera",
         ability: "bank:manage-accounts",
       },
+      {
+        href: "/notificaciones",
+        label: "Notificaciones masivas",
+        ability: "notification:send",
+      },
       { href: "/usuarios", label: "Usuarios", ability: "user:manage" },
       { href: "/operaciones", label: "Operaciones", ability: "db:manage" },
     ],