Fix planning: Row not JSON serializable

app.py

@@ -940,7 +940,7 @@ def delete_job(id):
 @app.route('/planning')
 def planning():
     conn = get_db()
-    printers  = conn.execute('SELECT * FROM printers ORDER BY id').fetchall()
+    printers  = [dict(r) for r in conn.execute('SELECT * FROM printers ORDER BY id').fetchall()]
     unscheduled = conn.execute('''
         SELECT j.*, c.name as client_name
         FROM jobs j LEFT JOIN clients c ON j.client_id=c.id