Add Jest tests for storage.controller (public-api)

[yash-pouranik]

We don’t have test coverage for apps/public-api/src/controllers/storage.controller.js. Please add a Jest
test file (e.g. apps/public-api/src/tests/storage.controller.test.js) following existing patterns in
apps/public-api/src/tests (see userAuth.controller.test.js for style).

Cover these cases:

• Upload success + failure (invalid file/size/quota)
• Delete success + not found/unauthorized
• Download success + missing file
• Unexpected error path (mock throw)

Mock storage provider + DB calls used by the controller.

Acceptance Criteria:
[] npm run test --workspace=public-api passes.

[yash-pouranik]

#72 already solved this