feat: add multiple vs single sample input mode for graphs

[berntpopp]

Description:
Introduce a toggle to switch between single and multiple input modes for graphs. In single mode, only one data point should be displayed. In multiple mode, users can input multiple data points and see them all plotted in the graph.

Acceptance Criteria:

• Toggle between single and multiple input modes.
• In single mode, only one data point is shown.
• In multiple mode, multiple data points are displayed on the graph.