Easily retrieve the number of "unhandled" scenarios

**What it's the actual situation on ARA ?**
I'm always frustrated when I try to get out KPIs for scenarios that are failed and not related to a problem (team KPIs)

**Describe the solution you'd like**
Would it be possible to have an API available for easily retrieve the number of "unhandled" scenarios per team / branch & cycle.

In the new API, have the ability to query:
- on the last run or on the ID of a previous run.
- on team number &/or team name
- on the handling "unhandled"
- on the cycle and branch (eg: develop / day)

The issue names no files or tests. Start by locating the existing API entry points and data models for runs, teams, branches, cycles, and scenario handling; verify how “unhandled” is represented. Done means an API can query the latest or a previous run by ID, filter by team, handling status, cycle, and branch, and return the number of matching scenarios.

Written by the indexing model from the issue text.