ui: statement activity page timepicker doesn't work with ranges less than an hour

Background:
CRDB allows users to configure the aggregation interval of sql stats, which defines the interval length in which sql stats are aggregated for a given fingerprint. As an example, setting the cluster setting `sql.stats.aggregation.interval='10m'` will create a new aggregation every 10 minutes for a given fingerprint.

Setting this setting allows granular introspection into sql stats by allowing sql stats tables to queried with smaller time slices.

Issue:
If a user defines a smaller aggregation interval (say 10m as mentioned above) db console will allow a user to specify a 10 minute window in the time picker, but the start and end timestamps used to request sql stats are those for the encapsulating hour.

Fix:
We should fix this so that the the api call to the backend sends the expected timestamps

initial slack conversation reporting the issue: https://cockroachlabs.slack.com/archives/C063CP41TG9/p1745853166239859

screenshot:


Jira issue: CRDB-49897