Problem: if your timezone offset is a non-whole number of hours, the Deployment>DAUs chart will fail to load.

Steps to reproduce:

• Set your browser TZ to India/Mumbai or some other fractional-offset TZ
• Load Depoyment>DAUs
• Observe sadness

Bug is here: https://github.com/coder/coder/blob/main/site/src/api/api.ts#L937

This ends up sending a request /v2/insights/daus?tz_offset=5.5 which is not accepted by the BE.

IIRC the usage metrics are bucketed by hour, so we probably need to round down to the closest hour.