[Feature request] Dashboard (aka "Quick Stats") view

Basically what title says, and what "other software" has - a dashboard, aka "Quick Stats". This means the following:

1. Count of how many services are up, down, maintenance, unknown and paused
2. List of last events from all services

The request is for a dashboard view showing service status counts and recent events. Start by examining the existing service status data models and event logging. Look at the current UI components to understand how to add a new view. Determine where to aggregate the counts and fetch the last events across all services. 'Done' means a new page or section displays the two requested pieces of information.

索引モデルが issue の本文から書いたものです。