fix: update form-data and multer to address security vulnerabilities

- Update form-data from 4.0.3 to 4.0.4 (fixes CVE GHSA-fjxv-7rqg-78g4)
- Update multer from 2.0.1 to 2.0.2 (fixes CVE GHSA-fjgf-rc76-4x9p)
- Both backend and frontend now have 0 vulnerabilities
- Tested upload functionality - all working correctly

These are patch updates with no breaking changes. The updates address:
- form-data: Critical vulnerability - unsafe random function for boundary
- multer: High vulnerability - DoS via unhandled exception

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

backend/package.json

@@ -28,7 +28,7 @@
     "express": "^4.18.2",
     "express-rate-limit": "^6.7.0",
     "express-validator": "^7.0.1",
-    "form-data": "^4.0.3",
+    "form-data": "^4.0.4",
     "handlebars": "^4.7.8",
     "helmet": "^7.0.0",
     "i18next": "^25.3.1",
@@ -39,7 +39,7 @@
     "jsonwebtoken": "^9.0.0",
     "knex": "^2.4.2",
     "mime-types": "^3.0.1",
-    "multer": "^2.0.1",
+    "multer": "^2.0.2",
     "node-cron": "^3.0.2",
     "nodemailer": "^6.9.1",
     "pg": "^8.16.3",