Weekly intervals in dashboards

### Problem Statement

Currently, when a time period of 14d > is selected, the maximum interval is 1 day. A customer has requested an interval of 7 days (likely only for timer periods >= 30 days) so that they can see weekly error rate week by week.

### Solution Brainstorm

Increase max interval to 7d for time periods >= 30d

### Product Area

Dashboards

No files or tests are named; start by locating the dashboard time-period and interval-selection handling. Confirm that periods of at least 30 days permit a 7-day interval and that the dashboard displays weekly error rates week by week.

Written by the indexing model from the issue text.