[BUG-02] Walk-in customers are charged the wrong late fee rate

[iuv1u]

Description: Late charges for Walk-in customers use the Corporate per-day rate ($2.00) instead of the correct Walk-in rate ($3.00).

Steps to Reproduce:

1. Rent a vehicle as a Walk-in customer
2. Return it after the due date
3. Check the late charge applied

Expected Result: Charge calculated at $3.00/day (Walk-in rate)
Actual Result: Charge calculated at $2.00/day (Corporate rate)

Severity: Medium
Priority: P2
Status: New
Environment: Chrome 125, Windows 11