[Bug]: Histogram visualization has multiple rendering and display issues

[jaimarothiya18]

What happened?

1. Overlapping bars: Multiple colored bars (red, yellow, blue) overlap making it hard to distinguish individual series
2. Y-axis scaling: The scale appears inconsistent or improperly calculated
3. Bar density: Bars are too tightly packed, creating visual clutter
4. Color contrast: Poor color differentiation between severity levels
5. Tooltip/legend: Unclear what each color represents

Expected behavior

• Clear, non-overlapping histogram bars
• Proper spacing between time buckets
• Distinct colors for different severity levels
• Readable Y-axis with appropriate scaling
• Tooltips showing exact counts on hover
• Legend indicating what each color represents

Steps to reproduce

1. Navigate to Explorer
2. Run a query that returns logs with multiple severity levels
3. Observe the histogram at the top of the results
4. Notice the overlapping bars and rendering issues

Environment

• General bug

Relevant log output

Additional context

No response