[AlexAndBear]

Description

When restoring a version fails, e.g. because the file is locked, we now show "Failed to restore version" instead of silently doing nothing.

Related Issue

• Fixes Restoring a file version fails silently #4100

How Has This Been Tested?

• test environment: unit tests (Vitest), browser tests (Playwright) against a local OpenCloud
• test case 1: unit: failed restore shows the error message and doesn't update the resource
• test case 2: browser: locked file (423) on desktop and Pixel 7 shows the error, no uncaught rejection; restoring an unlocked file still works

Types of changes

• Bugfix
• Enhancement (a change that doesn't break existing code or deployments)
• Breaking change (a modification that affects current functionality)
• Technical debt (addressing code that needs refactoring or improvements)
• Tests (adding or improving tests)
• Documentation (updates or additions to documentation)
• Maintenance (like dependency updates or tooling adjustments)