Add _wrap_label_text() method to split long variable names into multiple
lines at underscore boundaries (~15 characters per line). This prevents
overlapping labels for variables with lengthy names like
"wetlabsbb2fl_mass_concentration_of_chlorophyll_in_sea_water".

Changes:
- Add _wrap_label_text() helper method to wrap text at natural boundaries
- Apply wrapping to all colorbar labels (scatter, contour, and no-data plots)
- Reduce colorbar padding from default to 0.01 for more label space
- Place units on separate line with newline separator
- Reduce label font size from 9pt to 8pt where appropriate