feat: Implement Phase 2 cross-cutting services with email and notification enhancements

- Refactor email verification and password reset utilities to use new email service.
- Introduce email delivery queue and notification delivery model for better tracking.
- Enhance file validation and storage services for improved security and ownership management.
- Add cron job for cleaning inactive notifications with retention policy.
- Update document worker to handle document generation and storage more efficiently.
- Implement logging improvements in activity and log workers.
- Create comprehensive documentation for new API endpoints and services.
- Add unit tests for file validation and notification policies to ensure robustness.

app/services/email/email.service.js

@@ -0,0 +1,15 @@
+const crypto = require("crypto");
+const emailQueue = require("../../queues/email.queue");
+const db = require("../../models");
+const templates = {
+  otp: { subject: "Your ZUMRI login code" }, passwordChanged: { subject: "Your ZUMRI password was changed" },
+  passwordReset: { subject: "Reset your ZUMRI password" }, emailVerification: { subject: "Verify your ZUMRI email" }, welcome: { subject: "Welcome to ZUMRI" },
+};
+const send = async ({ templateKey, recipient, locale = "en", variables = {}, correlationId, notificationId, userId, eventId }) => {
+  if (!templates[templateKey]) throw new Error("Unknown email template");
+  const id = crypto.randomUUID();
+  await db.NotificationDelivery.create({ id, notificationId, userId, channel: "EMAIL", recipient, templateKey, status: "QUEUED" });
+  await emailQueue.add("send-email", { deliveryId: id, templateKey, recipient, locale, variables, correlationId }, { jobId: `email-${eventId || id}` });
+  return { deliveryId: id };
+};
+module.exports = { send, templates };