Insert pasted images as layers in document graph (#1418)

Changes:

Graph is evaluated on every viewport change
move all navigation logic into the viewport
reduce the number of js roundtrips
add canvas rendering
enable image pasting
various cleanups
Fix cache nodes being reset every evaluation

frontend/src/components/panels/Document.svelte

@@ -470,9 +470,7 @@
 							{@html artboardSvg}
 						</svg>
 						<svg class="artboards" style:width={canvasWidthCSS} style:height={canvasHeightCSS}>
-							<g id="transform-group" transform={$document.artworkTransform}>
-								{@html nodeRenderSvg}
-							</g>
+							{@html nodeRenderSvg}
 						</svg>
 						<svg class="artwork" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" style:width={canvasWidthCSS} style:height={canvasHeightCSS}>
 							{@html artworkSvg}