Fix offline sync priority, idempotent check state, and add loading spinner for meal plan import

app/database.py

@@ -1182,6 +1182,18 @@ def toggle_shopping_item(item_id: int) -> Optional[Dict[str, Any]]:
     return row
 
 
+def set_shopping_item_checked(item_id: int, checked: bool) -> Optional[Dict[str, Any]]:
+    """Setzt den Erledigt-Status eines Eintrags explizit auf True oder False."""
+    val = 1 if checked else 0
+    query = "UPDATE shopping_list SET checked = ? WHERE id = ?"
+    execute_query(query, (val, item_id), fetch="none", commit=True)
+    row = execute_query("SELECT * FROM shopping_list WHERE id = ?", (item_id,), fetch="one")
+    if row:
+        row["checked"] = bool(row.get("checked"))
+        row["display_source"] = clean_source_label(row.get("source", ""))
+    return row
+
+
 def delete_shopping_item(item_id: int) -> bool:
     """Löscht einen einzelnen Eintrag aus der Einkaufsliste."""
     query = "DELETE FROM shopping_list WHERE id = ?"