fix: avoid starting backend server during tests

[pggdev]

Description

#257

Updated the backend startup logic so importing app from server.js does not start the HTTP server.

Changes

• Moved app.listen(...) into an exported startServer function
• Added a direct-run guard so the server starts only when server.js is executed directly
• Kept app importable for Supertest without opening port 3001

Testing

• Ran backend tests with npm run test -- --run

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[gemini-code-assist]

Code Review

This pull request refactors the server startup logic in backend/src/server.js by encapsulating it within an exported startServer function and implementing a main module guard for direct execution. The review feedback suggests adopting the node: prefix for built-in module imports and using realpathSync to ensure the main module check is robust against symbolic links.

[gemini-code-assist]

In ECMAScript Modules (ESM), it is a best practice to use the node: prefix when importing built-in Node.js modules (e.g., node:url) to clearly distinguish them from npm packages. Additionally, I've included realpathSync from node:fs to support a more robust main module check in the direct-run guard.

import { pathToFileURL } from "node:url";
import { realpathSync } from "node:fs";

[gemini-code-assist]

The current check for the main module using process.argv[1] can be brittle. import.meta.url always contains the fully resolved path (with symbolic links resolved), whereas process.argv[1] might contain a symbolic link path depending on how the script was invoked. Using realpathSync ensures both paths are fully resolved before comparison, making the guard more robust across different deployment and execution environments.

Suggested change

	if (
	process.argv[1] &&
	import.meta.url === pathToFileURL(process.argv[1]).href
	) {
	startServer();
	}
	if (
	process.argv[1] &&
	import.meta.url === pathToFileURL(realpathSync(process.argv[1])).href
	) {
	startServer();
	}