Describe the bug
Issue spotted by @confluence

If we load an image in FK5 system, we see the x and y tick values are in HMS and DMS format, respectively. If we go to the settings dialog and change the format to DEG, DEG in the numbers tab and switch to the pan and zoom tab, we do not see the coordinate format is changed accordingly (the displayed values are still in HMS and DMS format).

To Reproduce
Steps to reproduce the behavior:

1. load an image with FK5/FK4/ICRS coordinate system
2. in the image viewer, we see axes values are in HMS and DMS format, respectively.
3. enable the image viewer settings dialog
4. go to the numbers tab and change the format HMS->DEG, DMS->DEG, we will see the axes values in the image viewer are changed accordingly
5. go to the pan and zoom tab, we expect to see the center coordinate format is changed to DEG too but it is not.

Expected behavior
in step 5 we expect to see the coordinate format in the pan/zoom tab is sync'd with the format defined in the numbers tab.

Screenshots or videos

Platform info (please complete the following information):

• OS [e.g. macOS Monterey]: macOS Ventura
• Browser [e.g. chrome, safari, electron app]: chrome
• Browser version [e.g. 22]: 106
• Backend branch [e.g. dev, v3b2 release]: dev
• Frontend branch [e.g. dev, v3b2 release]: dev