Karate Kata Referee Voting App (7 Judges + Main Tatami Controller)

I am looking for a small, rock-solid web application to be used during karate kata competitions.

The system must allow up to 7 judges to submit a verdict (RED or BLUE) and instantly push each vote to a central Tatami Controller screen.

Roles
1) Tatami Controller (Main Screen)
The only protected role (login or admin PIN required)
Create/open a session
Start a voting round
See live connection status of judges
Receive votes in real time
Manually lock/close voting (with optional auto-close when all 7 votes are received)
Display:
Individual judge votes
Total RED votes
Total BLUE votes
Highlight winner clearly
Reset for next match without losing system stability

2) Judges
No accounts required
Join via QR code or short session code
Assigned to a unique judge slot (1–7)
See only two large buttons: RED and BLUE
One-tap submit
Vote is locked after submission
Clear confirmation message after vote is accepted

Core Requirements
Fully web-based (no app store required)
Must work on tablets, laptops, and phones via browser
Real-time updates using WebSockets (preferred) or equivalent push mechanism
No manual refresh or polling
Minimal, clean interface optimized for live competition
Large, high-contrast results display readable from the edge of the mat

Reliability & Stability (Critical)
The system must handle:
Spotty or unstable sports-hall Wi-Fi
Automatic reconnection
Votes stored server-side (no loss on refresh)
Judge reconnecting sees “vote already submitted”
Controller page refresh does not lose match state
Duplicate vote prevention
Session isolation (no unauthorized devices joining)
Basic timestamp log for each vote

Deliverables
Judge page (session join, red/blue vote, confirmation, vote lockout)
Controller page (login/PIN, session creation, live vote stream, lock/close, totals, reset)
Lightweight backend handling real-time communication and state persistence
Deployment guide (how to run locally on a laptop in a venue LAN or on a simple cloud instance)
Brief test checklist for competition-day validation

Proposal Requirements
Please include:
Your proposed tech stack
How you will handle reconnection and prevent vote loss
Timeline and fixed price
Example of a similar real-time app