[Feat] Admin GUI: Updates Page

[derrickmehaffy]

Summary

The AdminUpdatesPage currently displays a "Coming Soon" placeholder. Implement an update management GUI that shows version info and allows admins to check for and install updates.

Features

Version Display

• Current installed version and build info (from BuildInfo)
• Build date and commit hash (if available)

Update Checking

• Check for updates against GitHub releases API
• Show latest available version
• Display changelog diff (what's new since current version)
• Indicate if current version is up-to-date, outdated, or pre-release

Update Installation

• Download latest release JAR from GitHub
• Install update (replace current JAR)
• Show download progress
• Prompt for server restart after update

Notification

• Optional notification to admins on join if an update is available
• Configurable auto-check interval

Existing Infrastructure

• AdminUpdatesPage.java — Placeholder page exists
• /f admin update — CLI update command already exists with backend logic
• GitHub releases API integration (if implemented in update command)

Origin

Roadmap Phase B.3 ("Coming Soon" admin page placeholder).