chore(deps): bump zod from 3.25.51 to 3.25.76 in /backend

---
updated-dependencies:
- dependency-name: zod
  dependency-version: 3.25.76
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

backend/package-lock.json

@@ -92,7 +92,7 @@
     "undici": "^7.11.0",
     "uuid": "^9.0.1",
     "winston": "^3.17.0",
-    "zod": "3.25.51"
+    "zod": "3.25.76"
   },
   "devDependencies": {
     "@eslint/compat": "1.2.9",