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/components/panels/Sidebar.tsx

@@ -165,7 +165,7 @@ function PendingDevicesPanel({ onNodeApproved }: { onNodeApproved: (nodeId: stri
     try {
       const nodeData = {
         label: device.hostname ?? device.ip,
-        type: device.suggested_type ?? 'generic',
+        type: (device.suggested_type ?? 'generic') as import('@/types').NodeType,
         ip: device.ip,
         hostname: device.hostname ?? undefined,
         status: 'unknown',