Line charts don't respect millisecond precision

## Description of the bug

Line-chart points with timestamps differing only by milliseconds stack on top of each other. Axis labels and tooltips do not display millisecond precision.

## Reproduction steps

1. Create a question using the following query:

```sql
SELECT cast('2025-03-30T00:00:00.000Z' as timestamp) AS created_at, 10 AS data_value
UNION ALL
SELECT cast('2025-03-30T00:00:00.500Z' as timestamp), 11
UNION ALL
SELECT cast('2025-03-30T00:00:01.000Z' as timestamp), 12
UNION ALL
SELECT cast('2025-03-30T00:00:01.500Z' as timestamp), 13
UNION ALL
SELECT cast('2025-03-30T00:00:02.000Z' as timestamp), 14
UNION ALL
SELECT cast('2025-03-30T00:00:02.500Z' as timestamp), 15;
```

2. Visualize the result as a line chart.

## Expected behavior

Points with distinct millisecond timestamps should render separately, and axis labels and tooltips should show millisecond precision.

## Logs

No logs provided.

## Diagnostic information

Metabase version: `master`

## Severity

P3

Start by reproducing the line chart with the SQL query in the issue and inspect the chart rendering and timestamp formatting entry points. Verify that sub-second points render separately and that axis labels and tooltips display millisecond precision.

Written by the indexing model from the issue text.