`colorbar [ERROR]: Time steps in seconds must be <= 60` if plotting done with a time X axis and the manually assigned colorbar (X) interval is > 60

`colorbar` seems to "inherit" X axis time units and does not allow tick interval greater than 60. This happens if plotting before colorbar is done with a time X axis. Please see the minimal failing code below.

The error occured only if the `colorbar` intervals are specified manually, automatic assignment of `colorbar` interval does not produce an error.

The expected behaviour is of course that the plot X axis settings has no effect on the `colorbar` interval settings so any manually assigned interval value works.

the minimal failing code:
```
gmt colorbar -R2017-01-01T/2025-01-01T/0/1 -JX10c/5c -Bxa500 -Cturbo -png colorbar
```

fails with the following error message:
```
colorbar [ERROR]: Time steps in seconds must be <= 60
colorbar [ERROR]: Option -B parsing failure. Correct syntax:

-B Specify both (1) basemap frame settings and (2) axes parameters.
Frame settings are modified via an optional single invocation of
-B[][+b][+g][+i[]][+n][+o/][+s]⏎
…[+t][+w[<pen>]][+x<fill>][+y<fill>][+z<fill>]
Axes parameters are specified via one or more invocations of -B[p|s][x|y|⏎
…z]<intervals>[+a<angle>|n|p][+e[l|u]][+f][+l|L<label>][+p<prefix>][+s|⏎
…S<secondary_label>][+u<unit>
<intervals> is composed of concatenated [<type>]<stride>[l|p] sub-
strings. See basemap documentation for more details and examples of all
settings.
colorbar [ERROR]: Offending option -Bxa500
```

if the interval is less than 60, the colorbar is plotted successfully:
```
gmt colorbar -R2017-01-01T/2025-01-01T/0/1 -JX10c/5c -Bxa50 -Cturbo -png colorbar
```
colorbar.png:

<img width="956" height="86" alt="Image" src="https://github.com/user-attachments/assets/c89303cb-e63b-4fba-849d-7adb3ce5e06d" />

the failing code above is expected to produce exactly the same result