Add a restore command for WP-CLI

[benoitchantre]

Is your feature request related to a problem? Please describe.
When there are a lot of images to restore, this is a tedious process using the media library, even with the bulk action.

Describe the solution you'd like
It would be very useful to have a restore subcommand to handle that task efficiently.

Additional context
A restore command is needed, because when you change the compression settings from smart to lossless, a lossless compression is applied on lossy images instead of restoring the original file instead before apply the lossless compression.

[Miraeld]

Pipeline delivery — wp imagify restore

PR: #1087
Branch: enhancement/922-add-a-restore-command

What was implemented

Added wp imagify restore [<contexts>...] WP-CLI subcommand following the synchronous approach from PR #1028.

New command:

wp imagify restore              # Restore all (library + custom folders)
wp imagify restore library      # WordPress media library only
wp imagify restore custom-folders

Architecture:

• RestoreCommand — new class, library → wp mapping via CONTEXT_MAP, optional repeating positional arg defaulting to all contexts
• Bulk::run_restore() — rewritten to synchronous loop over get_optimized_media_ids(), returns per-context {restored, errors, total} counts
• get_optimized_media_ids() — added to BulkInterface and implemented in WP, CustomFolders, Noop, NGG (latter two return [])
• AbstractBulk default removed — each concrete class must explicitly implement

Tests: 8 unit tests in RestoreCommandTest (WP_CLI fixture captures log/warning/error/success messages via static arrays)

Test results

Tests: 32, Assertions: 81, Risky: 13 (pre-existing PHP 8.4 deprecation in framework TestCase)
Errors: 0, Failures: 0
PHPCS: clean on all changed files