Alert - Allow "Recent Active Member" alert notifications to be scoped to a specific Team

### Problem Statement

When using the "Recent Active Member" notification option for alerts, it currently selects from the entire organization rather than being scoped to a specific team. This means team members outside the responsible team get pinged for issues they don't monitor, creating noise and alert fatigue across the company.

### Solution Brainstorm

Allow alert rules to optionally scope "Recent Active Member" to a selected team, so only recently active members within that team receive notifications. This would pair well with the existing team-based issue assignment workflow, and would benefit teams that use both Slack and Sentry integrations together to manage on-call or monitoring responsibilities.

### Product Area

Alerts

No files or tests are named. Start by locating the Alerts implementation for the "Recent Active Member" notification and the existing team-based issue assignment workflow; done means an alert rule can optionally select a team and notify only recently active members of that team.

Written by the indexing model from the issue text.