Lucky Jet Alert Web Tool

I want a lightweight web-based companion for 1Win’s Lucky Jet where players get a pop-up notification on the site a few seconds before I, as admin, decide a good moment to place a bet. No automated prediction logic is needed right now—everything is triggered manually from my side—so the core of the job is building:

• a clean admin panel where I can log in, write a short alert message, pick the lead-time (e.g., 5 s, 10 s) and hit “Send”
• real-time website notifications that reach every connected user instantly, even if they’ve switched to another browser tab
• a simple frontend page styled to match Lucky Jet’s color palette so users can keep it open alongside the game

Please implement using familiar web stacks (Node.js or PHP for the backend, WebSocket or Server-Sent Events for instant push, plus standard HTML/CSS/JavaScript on the client). Mobile-responsive layout is a must so players on phones get the same alert.

Acceptance criteria
– Admin trigger delivers the alert to all active sessions with no more than a 1-second delay during testing
– Users see both the audible and visual cue even if their tab is not in focus
– Basic authentication shields the admin panel

Once everything is deployed, hand over the source code and a short read-me so I can install it on my own server.