core: frontend: make the dashboard excellent

### Current behaviour

The dashboard displays a limited, fixed set of cards, without explanation or available actions to investigate/use something further.

### Expected or desired behaviour

At a high level, we want to
1. Make the interface configurable
- [ ] allow dynamically adding and removing widgets from services and Extensions
- [ ] allow moving and resizing widgets within the grid
1. Add key vehicle information
- [ ] branding and model
- [ ] a banner for critical warnings and required/recommended actions (e.g. calibrations and software updates)
- [ ] usage and maintenance details/statistics
- [ ] health states of connections (e.g. configured devices, bridges, streams, power supply, etc)
1. Integrate with the underlying services and other interface features
- [ ] allow clicking through to the most relevant service page for a widget
- [ ] allow pinning relevant widgets/components to the header bar

### Prerequisites

- [x] I have checked to make sure that a similar request has not already been filed or fixed.