fix: resolve printer model server-side for "Any Model" queue items (#435)

The previous fix passed target_model from the frontend, but this relied
on printer.model being set on the client. When a printer was added
without selecting a model (the field is optional), the frontend sent no
target_model parameter, causing the OR logic to be bypassed entirely —
the widget only queried printer_id=X and missed unassigned model-based
items.

The backend now looks up the printer's model from the database when
target_model isn't provided by the client, ensuring "Clear Plate &
Start Next" appears for model-based queue jobs regardless of how the
printer was configured.

backend/app/api/routes/print_queue.py

@@ -270,19 +270,30 @@ async def list_queue(
         if printer_id == -1:
             # Special value: filter for unassigned items
             query = query.where(PrintQueueItem.printer_id.is_(None))
-        elif target_model:
-            # Include both printer-specific items AND model-based (unassigned) items
-            query = query.where(
-                or_(
-                    PrintQueueItem.printer_id == printer_id,
-                    and_(
-                        PrintQueueItem.printer_id.is_(None),
-                        func.lower(PrintQueueItem.target_model) == target_model.lower(),
-                    ),
-                )
-            )
         else:
-            query = query.where(PrintQueueItem.printer_id == printer_id)
+            # Resolve effective model: prefer explicit param, fall back to printer's DB model.
+            # This ensures model-based "Any X" items are returned even when the frontend
+            # doesn't send target_model (e.g. printer.model is NULL on the client side).
+            effective_model = target_model
+            if not effective_model:
+                printer_row = (
+                    await db.execute(select(Printer.model).where(Printer.id == printer_id))
+                ).scalar_one_or_none()
+                effective_model = printer_row
+
+            if effective_model:
+                # Include both printer-specific items AND model-based (unassigned) items
+                query = query.where(
+                    or_(
+                        PrintQueueItem.printer_id == printer_id,
+                        and_(
+                            PrintQueueItem.printer_id.is_(None),
+                            func.lower(PrintQueueItem.target_model) == effective_model.lower(),
+                        ),
+                    )
+                )
+            else:
+                query = query.where(PrintQueueItem.printer_id == printer_id)
     elif target_model:
         query = query.where(func.lower(PrintQueueItem.target_model) == target_model.lower())
     if status: