feat: add color theme switching and expose admin theme to iframe apps

[Fabian Hüske (fabianhueske)]

Description

Adds color theme switching for Meteor apps and exposes the Administration's resolved theme to iframe apps through the Admin SDK.

Closes #1174
Closes #1129

Component library (#1174)

• mt-theme-select — a select component for choosing the application color theme (light, dark, system), with localized labels (en/de) and Storybook stories.
• useColorScheme composable — tracks the user's preference, resolves system against prefers-color-scheme, applies the resolved theme to a target's data-theme attribute, and persists the choice to localStorage.
  • Options: storageKey (set null to disable persistence), target, defaultScheme, applyToTarget.
  • Returns scheme, resolvedScheme, setScheme, and stop (to detach the OS-preference listener when used outside an effect scope; cleanup is automatic inside a component/effectScope).
• Exports the component, composable, and its types from the package entry point.

Admin SDK (#1129)

• context.getTheme() — resolves the current Administration theme; a system preference is always resolved to light or dark.
• context.subscribeTheme(cb) — fires whenever the resolved theme changes; returns an unsubscribe function.
• context.syncTheme({ target? }) — mirrors the resolved theme onto an element's data-theme attribute (document root by default), applies it immediately, and keeps it in sync. Subscribes before the initial fetch so a change during startup can't be missed.
• Documented in the Context API reference, including a minimal iframe app example.

Tests

• useColorScheme.spec.ts — defaults, system resolution, explicit preference, persistence, OS-change reactivity, custom target, applyToTarget: false, scope disposal, manual stop(), and disabled persistence.
• mt-theme-select.spec.ts — label rendering, options, re-emit, disabled, custom label.
• theme.spec.ts (admin-sdk) — getTheme, subscribe/unsubscribe, and syncTheme to document root and custom target.

Changesets

• @shopware-ag/meteor-component-library: minor
• @shopware-ag/meteor-admin-sdk: minor

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Project	Deployment	Actions	Updated (UTC)
meteor-component-library	Ready	Preview, Comment	Jun 23, 2026 1:02pm