🔧 Share the home section styling logic across identical components

[PierreBrisorgueil]

What — share the repeated section-styling logic across the home page's section components.

Why — eight components define an identical variant / containerStyle / sectionStyle trio plus the same theme data(). That is roughly 200 duplicated lines, and a change to the background rule currently means eight edits.

Scope — add src/modules/home/composables/home.sectionMixin.js and adopt it in the eight components whose trio is identical: about, articles, capabilities, cta, faq, features, services, steps.

These are Options-API components, so a Composition-API composable will not drop in — use a mixin. It lives under composables/ to match the module convention (billing, docs and legal each have one).

Do NOT convert these five — each differs, and converting breaks it (verified per file on master):

Component	Why excluded
contact	has no setup prop at all; its trio reads module config instead. The mixin would throw on render. Its data() also holds an unrelated key.
statistics	no variant, no containerStyle; its sectionStyle deliberately omits the background (supplied by the blur component). data() holds four animation keys.
social	sectionStyle adds an overflow rule and a gradient custom property the logo marquee depends on.
presentation	containerStyle adds padding and a glass style.
gallery	sectionStyle carries a theme-undefined guard for prerender safety.

hero and team.member have no trio at all.

Three of the eight (articles, capabilities, features) have extra data() keys beyond the theme one. Delete only the theme key — never the whole data() block. Drop data() entirely only where theme was its sole key.

Test-harness note: the mixin calls Vuetify's useTheme() in data(), which throws without a Vuetify install. There is no global Vuetify in the vitest setup, so a mount-based test must install Vuetify (and provide the config global) explicitly or it fails on harness rather than on logic.

Definition of done: home module tests pass, and the page is visually verified — this is in-scope visual work, so a runtime check is required, not optional. Confirm section backgrounds still alternate and that the five excluded components render unchanged.

Scope: validated 2026-07-28
Created via /dev:issue

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Baseline: line numbers and counts here were verified against master @ d246bc14 (2026-07-28). Master moves — re-verify against current master before starting; the invariants above are what must hold regardless of where the code has drifted to.

[PierreBrisorgueil]

🅿️ Parked by the 2026-07-30 board audit (P3, out of the drain queue).