Update Firestore database rules to restrict access

[izruff]

Currently, our database is in Test Mode (if I recall correctly) and is accessible from anywhere. We need to set the database rules so that only our domain nuansacp.org (and all of its subdomains e.g. tickets.nuansacp.org), and if possible our Vercel deployments, are allowed to send requests.

Please report on whether we can still access the DB from local environment and our Vercel previews.

This issue is to be completed outside of this repository. No PR needed.

[izruff]

UPD: I think from the following snippet from https://firebase.google.com/docs/firestore/security/rules-conditions, our env variables can bypass the rules, so yeah it's not to worry about.

Note: The server client libraries bypass all Cloud Firestore Security Rules and instead authenticate through Google Application Default Credentials. If you're using the server client libraries or the REST or RPC APIs, make sure to set up Identity and Access Management (IAM) for Cloud Firestore.

Also check this out: https://chatgpt.com/share/685223ae-cad4-800d-bb0f-36db25f40e35