Settings › Labels speaks the home page's language #9747

For: Settings › Labels (/:owner/:name/settings/labels) is how the owner names and colours the board's sorting, and it is the next settings page in the design pass.

Done looks like:

• [x] The labels page (src/web/pages/labels.ts) follows the opening principles of docs/DESIGN.md and reads like the settings pages already redone (Capacity, Features): each label a row with its colour, name and open count as a link to the issues it carries.
• [x] Nothing is lost: create, rename, recolour and delete still work as plain POST forms with a same-origin check and JavaScript off; delete still asks to confirm; the page fits a 390 px phone with no sideways scroll.
• [x] bun scripts/design-lint.ts passes, and so do test/labels*.test.ts.

Files: src/web/pages/labels.ts, and docs/design/areas/settings.md if a class is added. Risks: a label's colour is user input drawn into a style; keep it validated as a hex colour at the boundary, never echoed raw.

Reviewed pull #9809 at its head: ticked The labels page (src/web/pages/labels.ts) follows the opening principles of docs/DESIGN.md and reads like the settings pages already redone (Capacity, Features): each label a row with its colour, name and open count as a link to the issues it carries.; Nothing is lost: create, rename, recolour and delete still work as plain POST forms with a same-origin check and JavaScript off; delete still asks to confirm; the page fits a 390 px phone with no sideways scroll.; bun scripts/design-lint.ts passes, and so do test/labels*.test.ts..