fix: resolve TypeScript build errors blocking Docker image

- nodeColors.ts: add missing camera/printer/computer/cpl entries to Record<NodeType, NodeColors>
- CanvasContainer.tsx: use ConnectionMode enum instead of bare string literal
- export.ts: cast style object to Partial<CSSStyleDeclaration> for CSS custom property
- Sidebar.tsx: cast suggested_type to NodeType to satisfy NodeData type

frontend/src/utils/export.ts

@@ -8,9 +8,9 @@ export async function exportToPng(element: HTMLElement): Promise<void> {
   const dataUrl = await toPng(element, {
     backgroundColor: '#0d1117',
     style: {
-      // Exclude controls and minimap from the export
+      // Exclude controls from the export
       '--xy-controls-display': 'none',
-    },
+    } as Partial<CSSStyleDeclaration>,
   })
 
   const link = document.createElement('a')