refactor: improve ui/ux

[larskemper]

resolves #12775

[Copilot]

Pull Request Overview

This pull request significantly refactors the Shopware Migration Assistant UI/UX to improve user experience and provide clearer feedback during the migration process. The changes modernize the interface with better visual hierarchy, simplified navigation, and enhanced status messaging.

Key changes include:

• Revamped migration store with improved state management and validation messages
• Replaced assistant card with streamlined warning modal for currency/language mismatches
• Enhanced shop information display with better status indicators and action organization

Reviewed Changes

Copilot reviewed 63 out of 63 changed files in this pull request and generated 3 comments.

File	Description
migration.store.ts	Added new state properties, getters for validation messages, and enhanced migration control logic
en-GB.json / de-DE.json	Updated translations with clearer messages and reorganized modal text
Multiple HTML/SCSS files	UI improvements including better spacing, typography updates, and component restructuring
swag-migration-assistant component	Removed entire assistant card component in favor of simplified approach

Comments suppressed due to low confidence (1)

src/Resources/app/administration/src/module/swag-migration/page/swag-migration-history-detail/swag-migration-history-detail.scss:1

• There is a stray semicolon after the opening brace which is invalid CSS syntax.

@import "~scss/variables";

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