Consolidate Zustand Stores

**Is your feature request related to a problem? Please describe.**
We're planning to persist the application state. It would make it easier if there's only a single store we need to sync to the main process. Also, with zustand it's best practice to have a single monolithic store, possibly cut into slices. We currently have three stores.

**Describe the solution you'd like**
- Only a single store
- The state to persist can be easily cut out of the store
- If possible, also move more business logic from the render components into the store actions

**Describe alternatives you've considered**
A single store with all data to persist and another store with the rest.

**Additional context**
Add any other context or screenshots about the feature request here.

Start by locating the three existing Zustand stores and the render components that use them. Determine how the state intended for persistence can be separated and whether business logic can move into store actions; done means the application uses one store with a clear persistence boundary.

Written by the indexing model from the issue text.