This pull request introduces improvements to the flow board's node placement logic, visual theme updates, and minor UI behavior changes. The most significant updates include automatic placement and wiring of a "delay" node when a placeholder is used, adjustments to flow layout margins and default coordinates, and enhancements to the accent color for better visual distinction.

Flow board logic and node placement:

• Automatically places and wires a "delay" node when a placeholder is added to the flow board, including connecting its input and output pins to the new layer. [1] [2]
• Changes the default index for input pins on new placeholder nodes from 0 to 1 for consistency.
• Ensures the dropped pin state is cleared after placing a placeholder, preventing unintended connections.

Flow layout and initial coordinates:

• Updates flow layout margin calculations and default layer coordinates to provide more spacing and better initial positioning of layers. [1] [2]

Visual theme and accent color:

• Updates the accent color in both CSS and theme JSON for improved visibility and distinction in the UI. [1] [2]
• Applies the accent color to the layer node header for a more visually prominent appearance.

Minor UI behavior:

• Removes redundant context menu close logic to avoid unnecessary side effects when the placeholder dialog is closed.