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.

tests/unit/storage.service.test.js

@@ -0,0 +1,21 @@
+describe("Phase 2 file validation", () => {
+  beforeEach(() => jest.resetModules());
+  test("detects a valid PNG and creates checksum/safe name", () => {
+    const { validateUpload } = require("../../app/services/storage/file-validation.service");
+    const buffer = Buffer.concat([Buffer.from([0x89,0x50,0x4e,0x47,0x0d,0x0a,0x1a,0x0a]), Buffer.from("payload")]);
+    const result = validateUpload({ buffer, mimetype: "image/png", originalname: "../unsafe name.svg" });
+    expect(result.mimeType).toBe("image/png"); expect(result.safeName).toBe("unsafe_name.png"); expect(result.checksum).toMatch(/^[a-f0-9]{64}$/);
+  });
+  test("rejects claimed MIME that disagrees with magic bytes", () => {
+    const { validateUpload } = require("../../app/services/storage/file-validation.service");
+    expect(() => validateUpload({ buffer: Buffer.from("not an image"), mimetype: "image/png", originalname: "x.png" })).toThrow("does not match");
+  });
+  test("rejects empty files", () => {
+    const { validateUpload } = require("../../app/services/storage/file-validation.service");
+    expect(() => validateUpload({ buffer: Buffer.alloc(0), mimetype: "image/png", originalname: "x.png" })).toThrow("Empty");
+  });
+  test("builds controlled owner/date keys without original filenames", () => {
+    const { createObjectKey } = require("../../app/services/storage/storage.service");
+    expect(createObjectKey({ ownerId: "usr_1", mimeType: "application/pdf", purpose: "document", now: new Date("2026-09-03T00:00:00Z"), id: "fixed" })).toBe("documents/usr_1/2026/09/fixed.pdf");
+  });
+});