changing logo for light mode

Issue:
Logo appears greyed out in light mode.

Proposed fix:
Use the current (light) logo only in dark mode, and apply a darker version (#444950) for light mode to ensure better contrast and visibility. 

<img width="1850" height="867" alt="Image" src="https://github.com/user-attachments/assets/47baeb0d-550c-483c-b590-1ce0bfacd919" />