Add UnifiedPush notification system with Ktor server

Implement push notifications via UnifiedPush protocol for timer-based
events (adventure completion, character evolution, special missions,
BE training, item effects). Includes:

- Ktor server module for timer scheduling and push delivery
- Android UnifiedPush 3.x PushService integration
- Push preferences in DataStore, HTTP client for server communication
- Settings UI for server URL, push toggle, and test notifications
- Timer registration in Adventure, Home, and Scan controllers
- Docker support for server deployment
- CLAUDE.md and editor rules for project conventions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>