Better Placeable Sell Prices

This script enhances the selling experience for placeables by offering better prices.
Players benefit from a 1-month grace period after placing a placeable.
If sold within this period, 100% of the purchase cost is refunded.
After 1 month, the refund drops to 80% and continues to decrease monthly, similar to the base game mechanics.
Note: Landscaping costs are not refunded.