Add game lifecycle management and instance import/export tools (#117)

## Summary by Sourcery

Add centralized game process and instance lifecycle management, shared
cache-aware path resolution, and instance import/export/repair
capabilities across backend and UI.

New Features:
- Track a single running game process in the backend, expose stop-game
control, and emit structured game-exited events with instance and
version context.
- Introduce instance path resolution that supports shared caches for
versions, libraries, and assets, and use it across game start, install,
and version management APIs.
- Add import, export, and repair operations for instances, including
zip-based archive support and automatic recovery of on-disk instances.
- Expose new instance lifecycle and repair APIs to the frontend and wire
them through the client and instance store.
- Add per-instance start/stop controls in the instances view and
instance selection in the bottom bar for launching games.

Enhancements:
- Guard instance operations with per-instance locks and track active
operations such as launch, install, delete, and import/export.
- Improve handling of Microsoft login errors and polling status, with
clearer user feedback and safer interval management.
- Simplify config mutation during shared cache migration and centralize
instance directory resolution in the backend.
- Initialize a game lifecycle listener at app startup to keep UI state
in sync with backend game exit events.

Build:
- Configure the Vite dev server to use a fixed localhost host and port
for the UI dev environment.

0 files changed, 0 insertions, 0 deletions