Updater improvements, config UI enhancements, improved annoucement system, fixes and localization

[JacksonTheMaster]

This PR improves the automatic update system and config page UI, several localization and bug fixes, and some general polish.

Auto-Updater improvements

• Refactored and split updater code into separate files for maintainability
• Added periodic update polling during runtime (every 6 hours)
• Added server-side API endpoints to check for updates
• Implemented localized frontend update modal to notify users of available updates and allow in-app updating.

UI/UX Improvements

Config page overhaul:

• New sliding tab structure
• improved terminology
• Added (but temporarily hidden) SLP tab preparation.
• Moved detection manager into tab style.
• Fixed broken button icons (I broke them in 5.9.1 with the xmas design) and some mobile styling issues.

Improved main dashboard annoucements

• Improved announcements system to display multiple announcements if needed.

Bug Fixes & Reliability

• Fixed world saved detection and notifications (debounced to prevent spam, cleaner timestamps; reported by @steven10172, thx).
• Added retry once logic and better error handling for SteamCMD exit status 8 (especially during first setup; thanks to Seneram (Discord handle)).
• Fixed missing localization on setup finalize button and setup info text (fixes Missing localization in setup track #121).
• Fixed config page mobile styles in several places.

Localization

• Updated/added messages in de-DE, en-US, and sv-SE files (local IP guidance, setup track, update modal, general clarity improvements).

Minor changes

• Updated README and Wiki (finally)
• Fixed preview buttons to point to v4 live demo again (as it's still close enough).
• Added direct download buttons by improving the github pages page (Now the "Download Page"
• Changed copyright/year references from 2025 → 2026.

[JacksonTheMaster]

reviewd, lgtm