Reporter asked for an option to order printed label sheets by colour
instead of spool number so multi-colour rolls group related colours
together physically on the sheet.
Backend (labels.py) already preserves caller order, so this is
frontend-only. LabelTemplatePickerModal gains a "Sort: By ID / By
colour" chip pair next to the material filter. Colour mode converts
each spool's rgba to HSL: chromatic colours (s >= 0.1) cluster in
bucket 0 ordered by hue 0..360, achromatic colours go in bucket 1
ordered by lightness so neutrals trail the rainbow black -> white.
Stable tiebreaker on spool ID.
Also fixes a latent issue exposed by the same code: the submit was
always re-sorting selected IDs ascending, which would have clobbered
any frontend order. Submit now uses sortedSpools.filter().map() so
the visible order flows through to the PDF.
Session-only state; toggle resets to "By ID" each time the modal
opens. 3 new i18n keys translated across all 8 locales (parity 4852
leaves). 2 new modal tests pin the colour-sort payload order and
the unchanged ID-default. 17 modal tests + i18n parity + build all
green.
maziggy
fcd1801aab