- Enhanced skip objects feature with visual improvements and better UX

- Skip Objects Modal:
    - Object ID markers overlaid on preview image (grid layout)
    - Large prominent ID badges to match printer display
    - Info banner explaining to match IDs with printer screen
    - Layer warning when skip unavailable (layer <= 1)
    - Red badge on button showing skipped count
    - Preview image now shown when paused (not just running)
    - Close with ESC key or click outside modal
    - Full light/dark theme support

  - Backend:
    - Extract object positions from 3MF (include_positions=True)
    - API returns x/y coordinates for objects (when available)
    - Parse s_obj from printer MQTT for skipped state persistence
    - Cover URL available in PAUSE/PAUSED states

  - Tests:
    - Added test for objects with position data

frontend/src/api/client.ts

@@ -163,6 +163,8 @@ export interface PrinterStatus {
   mc_print_sub_stage: number;
   // Timestamp of last AMS data update (for RFID refresh detection)
   last_ams_update: number;
+  // Number of printable objects in current print (for skip objects feature)
+  printable_objects_count: number;
 }
 
 export interface PrinterCreate {
@@ -1289,6 +1291,24 @@ export const api = {
       method: 'POST',
     }),
 
+  // Skip Objects
+  getPrintableObjects: (printerId: number) =>
+    request<{
+      objects: Array<{ id: number; name: string; x: number | null; y: number | null; skipped: boolean }>;
+      total: number;
+      skipped_count: number;
+      is_printing: boolean;
+    }>(`/printers/${printerId}/print/objects`),
+
+  skipObjects: (printerId: number, objectIds: number[]) =>
+    request<{ success: boolean; message: string; skipped_objects: number[] }>(
+      `/printers/${printerId}/print/skip-objects`,
+      {
+        method: 'POST',
+        body: JSON.stringify(objectIds),
+      }
+    ),
+
   // AMS Control
   refreshAmsSlot: (printerId: number, amsId: number, slotId: number) =>
     request<{ success: boolean; message: string }>(