How to get these values:
1. Go to console.firebase.google.com → Create/open a project
2. Click Add app → Web (the </> icon)
3. Copy the config values shown (apiKey, projectId, etc.)
4. In Firestore → Rules, set: allow read, write: if true;
5. Your data will be saved at: invoices/ and quotations/
Config is stored in your browser's localStorage. Never shared externally.