Allow configuring Nextcloud domain from settings

[SmoothMC]

Summary

• add persistent Nextcloud domain storage backed by electron-store and load Deck automatically when configured
• expose a settings window and preload bridge so the domain can be entered on first start or changed later
• refresh the local renderer UI to provide a guided form for setting the domain and update dependencies accordingly

Testing

• npm install (fails: registry access forbidden)

---

https://chatgpt.com/codex/tasks/task_e_69032e40b658832c8584c2cd2e5df94d