Simple dashboard for showing money fluctuation in defined period, per account

First of all, thank you very much for this awesome application. It works like a charm on android phones

I am curious about one feature: Simple dashboard for showing money fluctuation in defined period, per account. While this feature might not be useful if you are using cone to input data and then sync it to xyz periodically, if you use cone for all ledger related operations on phone, while moving around, then simple dashboard with details on how much was spent per account in defined period would be very nice to have.

Think of it in `ledger` sense like this:

```
ledger -M --period-sort t reg -s ^expenses
```

Or even simpler:

```
ledger -M reg expenses
```

That would provide on-the-go quick info about accounts and usage on the phone.

Details:
- cone version 0.2.20
- android 12

The issue names no source files, tests, or entry points. Start by locating the existing account and ledger views, then define the period selector and per-account fluctuation display; done means the dashboard reports results consistent with the supplied ledger examples on Android.

Written by the indexing model from the issue text.