🍒runners/calculator: set timeout to prevent allocating huge memory

This is not exactly a memory leak. The extreme expression simply requires huge amounts of memory to calculate.

The calculator runner is problematic since it does not specify a time limit for calculations, and does not even abort calculations after the window has been closed (a simple example of this is the expression 123456789!).

Fixes https://github.com/Qalculate/libqalculate/issues/527

BUG: 468084 FIXED-IN: 5.27.5

(cherry picked from commit 3f3bea07)