Pin calc stats to sidebar

[KenManDev]

Fixes #1731

Description of the problem being solved:

The Calcs tab can be difficult to read at a glance when trying to monitor a small number of specific values. This adds a lightweight way to keep selected calculation values visible without requiring a custom layout system.

• Added the ability to pin/unpin Calcs tab values to the left sidebar by right-clicking them.
• Left-click behavior is unchanged and still pins/preserves the breakdown popup within calcs tab.
• Added a "Clear Pinned Stats" button next to the Calcs tab search field.
• Added helper text explaining that right-clicking a stat pins it to the sidebar.

Steps taken to verify a working solution:

• Verified that right-clicking a Calcs tab value adds it to the pinned section in the sidebar.
• Verified that right-clicking the same value again removes it from the pinned section.
• Verified that the pinned sidebar values use the existing calc formatting and update correctly.
• Verified that left-clicking still preserves the existing breakdown popup behavior.
• Verified that the "Clear Pinned Stats" button removes all pinned values.

Before screenshot:

After screenshot: