Fix/test app import mismatch

[mrunalC27]

Description

Closes #862. api/index.js exports the Express app as the default export (module.exports = app), but tests/api.test.js was importing it as a named export (const { app } = require(...)), so app in the tests was always undefined.

Changes

• tests/api.test.js: changed the import to match the actual export shape (const app = require('../api/index')).
• api/index.js: guarded startServer(PORT) so it doesn't run when NODE_ENV === 'test', preventing a real TCP port from binding during test runs (this was causing the TCPSERVERWRAP open-handle warning and the "log after tests are done" warning).

Went with fixing the test import rather than restructuring the api/index.js export, since vercel.json points @vercel/node directly at api/index.js and expects a callable export — wrapping it in { app, handler } would've broken the Vercel deployment path.
Confirmed tests/api.test.js is the only consumer of this import.

Testing

npm test — all 4 tests now pass, no open handles, no stray logs.

[vercel]

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