The DM needs to connect this app to Firebase so everyone's availability syncs live.
Step 1 — Create a free Firebase project
Go to console.firebase.google.com and click Add project. Give it any name (e.g. adventurers-ledger). You don't need Google Analytics.
Step 2 — Add a web app
In your project, click the web icon </>, give it a nickname, and click Register app. You'll see a firebaseConfig object — copy the whole thing.
Step 3 — Enable Realtime Database
In the left sidebar go to Build → Realtime Database → Create database. Choose any region. When asked about rules, select Start in test mode (you can lock it down later).
Step 4 — Paste your config below
Paste the firebaseConfig object (just the { ... } part, or the whole snippet — both work).
Connecting to the realm...
✦ The Adventurer's Ledger ✦
Who are you?
Select your character to mark your availability
Live sync active
✦ The Adventurer's Ledger ✦
Set a 4-digit PIN so only you can edit your slots.