Add multiplayer scoreboard mode with Firebase signaling

[Copilot]

Adds a dedicated scoreboard display for tablets and a roller interface for phones to submit dice rolls, using Firebase Realtime Database for synchronization.

New Components

• Scoreboard Mode (scoreboard.html/css/js) - Tablet-optimized display showing bank, round, turn, player scores. Creates 4-char room codes for joining.
• Roller Mode (roller.html/css/js) - Phone interface to join games and submit dice rolls to the scoreboard.
• Multiplayer Manager (multiplayer.js) - Handles room creation, state sync, and roll/bank request forwarding via Firebase.

Changes

• Updated index.html with mode selector links
• Updated sw.js cache manifest for new files
• Updated README.md with multiplayer setup docs

Setup Required

Replace placeholder values in firebase-config.js with your Firebase project credentials:

const firebaseConfig = {
    apiKey: "YOUR_API_KEY",
    databaseURL: "https://YOUR_PROJECT.firebaseio.com",
    // ...
};

Screenshots

Main Page

Scoreboard Mode

Original prompt

I need a separate score board, and prep to host multi player with webrtc. Let's set this up using firebase as a signaling server.

for the first new iteration, I want a mode where I can set up a tablet as a scoreboard, showing the bank, round number, turn, and each players score. then one or more phones will connect to register roll numbers.

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