Project Forecast Lines Bokeh Chart

This module adds a new reporting screen called Forecast Reporting, available in the menu of the Project Forecast module. It is a wizard-style form: you choose a start date, a number of months, a time granularity (day, week or month), one or more employees and, optionally, one or more projects. The chart is then drawn directly on the screen.

• The chart shows one stacked bar chart per selected employee, with one coloured bar segment per project, so you can see how each person's forecasted workload is split across projects over time.
• When you select projects, all employees assigned to tasks of those projects are automatically added to the employee selection.
• Forecasts that are not linked to a project are shown as "Available" when positive and as "Overload" when negative, and these two categories are placed first in the legend.
• Forecast lines with no employee are grouped under "Not assigned to an employee" and shown last.
• The chart uses the forecast data of the project forecast lines, grouped by the chosen granularity, and the legend can be clicked to hide or show a project.
• If no data matches the selection, a placeholder chart with the message "Nothing to plot. Select some employees" is displayed.

The module relies on the forecast line data and on the Bokeh chart widget to render the graph. It does not create any new business records; it is purely a reporting tool.