line chart on backlog trace legend interferes with the chart title

1. find open vs completed chart function in chart.py module
2. move labels horizontal below chart or to a place that doesn't overlap with chart title

Open chart.py and find the function that builds the open-versus-completed chart. Inspect how the legend labels are positioned, then adjust their placement so they no longer overlap the chart title. Done means the chart displays its labels horizontally below the chart or in another non-overlapping location.

Written by the indexing model from the issue text.