Cleanup: Removing monkeypatches for litegraph logic (#5902)

## Summary

Putting the litegraph specific pieces into litegraph itself, using the
CanvasGraph and LiteGraphGlobal to coordinate options.

This was one part of the Image Previews reloading/calculating with every
canvas draw.

## Review Focus

Is this keeping things decoupled enough?
Is this the right place to put things?
Are there assumptions about the options that I'm missing here?

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5902-WIP-Removing-monkeypatches-for-litegraph-logic-2816d73d3650818b860ec73579b89b54)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

src/lib/litegraph/src/LGraphNode.ts

@@ -7,6 +7,7 @@ import {
 } from '@/renderer/core/canvas/litegraph/slotCalculations'
 import { useLayoutMutations } from '@/renderer/core/layout/operations/layoutMutations'
 import { LayoutSource } from '@/renderer/core/layout/types'
+import { type ColorAdjustOptions, adjustColor } from '@/utils/colorUtil'
 
 import type { DragAndScale } from './DragAndScale'
 import type { LGraph } from './LGraph'
@@ -302,13 +303,25 @@ export class LGraphNode
 
   /** The fg color used to render the node. */
   get renderingColor(): string {
-    return this.color || this.constructor.color || LiteGraph.NODE_DEFAULT_COLOR
+    const baseColor =
+      this.color || this.constructor.color || LiteGraph.NODE_DEFAULT_COLOR
+    return adjustColor(baseColor, { lightness: LiteGraph.nodeLightness })
   }
 
   /** The bg color used to render the node. */
   get renderingBgColor(): string {
-    return (
+    const baseBgColor =
       this.bgcolor || this.constructor.bgcolor || LiteGraph.NODE_DEFAULT_BGCOLOR
+    const adjustments: ColorAdjustOptions = {
+      opacity: LiteGraph.nodeOpacity,
+      lightness: LiteGraph.nodeLightness
+    }
+
+    return adjustColor(
+      this.mode === LGraphEventMode.BYPASS
+        ? LiteGraph.NODE_DEFAULT_BYPASS_COLOR
+        : baseBgColor,
+      adjustments
     )
   }