Add chamber light control to printer card

- Add light toggle button next to camera button at bottom of card
  - Custom ChamberLight SVG icon with on/off states (yellow fill + rays when on)
  - Backend endpoint: POST /printers/{id}/chamber-light?on=true|false
  - Optimistic UI update for instant feedback
  - Works on all Bambu Lab printers (X1, P1, A1, H2D)
  - H2D dual chamber lights controlled together

Closes #67

frontend/src/api/client.ts

@@ -1333,6 +1333,12 @@ export const api = {
       method: 'POST',
     }),
 
+  // Chamber Light Control
+  setChamberLight: (printerId: number, on: boolean) =>
+    request<{ success: boolean; message: string }>(`/printers/${printerId}/chamber-light?on=${on}`, {
+      method: 'POST',
+    }),
+
   // Skip Objects
   getPrintableObjects: (printerId: number) =>
     request<{