fix: queue stuck on "Busy" for "Any Model" jobs (#435)

When a print was queued with "Any [Model]", the queue widget only
queried items with printer_id=X after dispatch, missing the next
pending model-based item (printer_id IS NULL, target_model="P1S").
The "Clear Plate & Start Next" button never appeared, leaving the
scheduler stuck reporting "Busy".

Add optional target_model query parameter to GET /queue/. When
combined with printer_id, uses OR logic to also return unassigned
items whose target_model matches. The frontend now passes the
printer's model through PrinterQueueWidget to this query.

backend/app/api/routes/print_queue.py

@@ -8,7 +8,7 @@ from pathlib import Path
 
 import defusedxml.ElementTree as ET
 from fastapi import APIRouter, Depends, HTTPException, Query
-from sqlalchemy import func, select
+from sqlalchemy import and_, func, or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import selectinload
 
@@ -248,6 +248,9 @@ def _enrich_response(item: PrintQueueItem) -> PrintQueueItemResponse:
 async def list_queue(
     printer_id: int | None = Query(None, description="Filter by printer (-1 for unassigned)"),
     status: str | None = Query(None, description="Filter by status"),
+    target_model: str | None = Query(
+        None, description="Filter by target model (also includes model-based items when combined with printer_id)"
+    ),
     db: AsyncSession = Depends(get_db),
     _: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_READ),
 ):
@@ -267,8 +270,21 @@ 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)
+    elif target_model:
+        query = query.where(func.lower(PrintQueueItem.target_model) == target_model.lower())
     if status:
         query = query.where(PrintQueueItem.status == status)