Added a clear first point distinction when drawing a custom shape: if the mouse cursor is near the beginning of a line (the shape can be closed), the first point is drawn in yellow and larger. This allows the user to see when they can close the shape with a single click. The code has been compiled and is ready to use. The functionality works as expected.
Introduces a 'visible' property to layers and updates all relevant logic to support toggling layer visibility. Adds visibility toggle icons to the layers panel using a new IconLoader utility, with SVG and fallback canvas icons. Updates rendering, selection, and batch preview logic to respect layer visibility. Also improves blend mode menu UI and ensures new/pasted layers are always added on top with correct z-index.
