Add light variants for red, blue, yellow, pink, orange colour schemes

Extends ticket 048's light_green pattern (light-inverted surface/border/text
scale + light's neutral danger colours, same base and accent hues as the
dark-surfaced counterpart) to the remaining five colour schemes across all
six files that must stay in sync: index.css, themes.ts, api.ts, settings.rs,
useSettingsPanel.ts, and NavMenu.tsx.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

tickets/056-light-variants-for-remaining-colour-schemes.md

@@ -1,77 +0,0 @@
-# 056 — Add `Light *` variants for the remaining colour schemes
-
-## Summary
-
-Ticket 048 already added one light-surfaced variant, `light_green`
-(`webapp/src/lib/themes.ts:231-254`, commit `5371d3e`: "Adds a new
-'Light Green' scheme (light-surfaced, same green/magenta hue family as
-'Green') selectable alongside the existing built-ins"). The wishlist
-comment that prompted 048 — "we need a `Light Green` alongside `Green`"
-— is now clarified as applying to *every* colour scheme, not just green:
-the current built-in set is `dark`, `light`, `red`, `green`, `blue`,
-`yellow`, `pink`, `orange`, `light_green`
-(`webapp/src/lib/themes.ts:38-255`), so `red`, `blue`, `yellow`, `pink`,
-and `orange` still have no light-surfaced counterpart.
-
-Adding a scheme is not fully data-driven from `themes.ts` alone — six
-files must be kept in sync per scheme, per the no-build-step-links-them
-comment at `webapp/src/index.css:1-7`:
-
-1. `webapp/src/index.css:264-300` — the `html.light_green` CSS block is
-   the reference recipe: same hue + same accent hues as the dark
-   counterpart, but with `light`'s inverted (high-lightness)
-   surface/border/text scale, and `light`'s hue-neutral danger colors
-   (comment at `index.css:264-268` documents this explicitly).
-2. `webapp/src/lib/themes.ts:231-254` — the matching `BUILTIN_THEMES`
-   entry (used for CSS export/download and validation).
-3. `webapp/src/lib/api.ts:83-93` — the `ColorScheme` TS union type.
-4. `src/settings.rs:30-42` — the matching Rust `ColorScheme` enum variant,
-   with `#[serde(rename = "light_<name>")]`.
-5. `webapp/src/lib/useSettingsPanel.ts:24-34` — `THEME_CLASSES`, used to
-   apply/strip the `html.*` class.
-6. `webapp/src/components/NavMenu.tsx:20-31` — `COLOR_SCHEMES`, which
-   drives the picker UI; `schemeLabel()` (`NavMenu.tsx:34-35`) already
-   auto-titles `light_red` → "Light Red" by replacing underscores, so no
-   extra label wiring is needed once a name is added to this array.
-
-`PanelChart.tsx`'s multi-accent `color-mix()` series-color logic (touched
-by ticket 048) is generic per-theme rather than per-scheme-name, so it
-likely needs no changes — worth a quick check while implementing, not
-expected to require edits.
-
-Tickets 047/048's original files were deleted on implementation (git
-history only shows their removal commits, `5cb2dfd`/`7c331e7`; bodies
-aren't recoverable), but commit `5371d3e`'s message and the resulting
-`light_green` block are sufficient as the template.
-
-## Scope
-
-- Add `light_red`, `light_blue`, `light_yellow`, `light_pink`, and
-  `light_orange` following the exact `light_green` recipe: same base
-  hue and accent-hue choices as the corresponding dark-surfaced scheme,
-  `light`'s inverted surface/border/text lightness scale, `light`'s
-  neutral danger colors.
-- Update all six files listed above for each new scheme:
-  `webapp/src/index.css`, `webapp/src/lib/themes.ts`,
-  `webapp/src/lib/api.ts`, `src/settings.rs`,
-  `webapp/src/lib/useSettingsPanel.ts`, `webapp/src/components/NavMenu.tsx`.
-- Verify `schemeLabel()` produces correct titles ("Light Red", "Light
-  Blue", etc.) without additional label-mapping code.
-- Spot-check `PanelChart.tsx`'s series-color logic against one new light
-  scheme to confirm it needs no changes (or fix it if it does).
-
-## Acceptance criteria
-
-- All five new schemes are selectable in the settings picker
-  (`NavMenu.tsx`), persist correctly, and are downloadable as CSS via
-  the existing "download built-in theme" path.
-- Each new scheme's CSS block round-trips through `Settings`
-  serialization/deserialization (`src/settings.rs`) without errors,
-  verified with a test analogous to any existing `ColorScheme`
-  serialization test.
-- `make build` and `make lint` pass with the new schemes added.
-
-## Depends on
-
-048 (implemented; this ticket extends its established pattern to the
-remaining base hues).