Ensure float conversion in exponentiation

Explicitly converts 'other' to float in the exponentiation method to avoid type errors when using non-float numeric types.

Author: Zeroto521

src/pyscipopt/expr.pxi

@@ -257,7 +257,7 @@ cdef class Expr:
             raise TypeError(f"Unsupported base type {type(other)} for exponentiation.")
         if other <= 0.0:
             raise ValueError("Base of a**x must be positive, as expression is reformulated to scip.exp(x * scip.log(a)); got %g" % other)
-        return exp(self * log(other))
+        return exp(self * log(float(other)))
 
     def __neg__(self):
         return Expr({v:-c for v,c in self.terms.items()})