Fix v5 folder history creation

[GitKa3sar]

V5 folder creation fails when Log plugin validates folder history

This pull request is a (multiple allowed):

• bug fix
• change of existing behavior
• new feature

Checklist

• User stories are present (given, when, then format)
• Unit tests are passing
• Selenium tests are passing (not run; this is a server-side history regression)
• Check style is not triggering new error or warning

User story

Given that encrypted metadata is enabled and the Log plugin records entity history,
when a user creates a v5 folder without a plaintext name,
then the folder and its audit history should be created successfully without storing a plaintext name.

Given a v4 folder history payload,
when the plaintext name is missing,
then the existing validation error should still be returned.

What you did

Fixes #617.

• Added a v5 validator for folder history that does not require the v4 plaintext name.
• Selected that validator only when the source folder contains encrypted metadata.
• Made folders_history.name explicitly nullable while preserving its 256-character limit.
• Added model regression coverage for v5 and for the unchanged v4 requirement.
• Added an integration regression test covering Model.afterSave, ActionLogsModelListener, detailed folder history, and entities_history.

Verification

• FoldersHistoryTableTest: 4 tests, 8 assertions.
• EntitiesHistoryCreateServiceTest: 2 tests, 7 assertions.
• MetadataFoldersCreateControllerTest: 15 tests, 101 assertions.
• PHP CodeSniffer on all changed files: passed.
• PHPStan on all changed PHP source and tests: passed.

[CLAassistant]

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