Feature/wiki prevent ancestor reversion

[NishikawaKoharu]

Purpose

Prevent wiki "ancestor reversion" caused by stale local drafts after closing the editor without saving. This PR adds the close-confirmation UI and Japanese translations. Editor behavior is in the companion PR on RDM-wiki-develop.

Changes

• Add a close confirmation modal (closeConfirmModal) with Cancel / Discard / Save and Close
• Add Japanese translations for the new modal strings

QA Notes

• Does this change require a data migration? If so, what data will we migrate?
  • No
• What is the level of risk?
  • Low–medium (UI/i18n only in this repo; behavior depends on the wiki editor PR)
• Any permissions code touched?
  • No
• Is this an additive or subtractive change, other?
  • Additive (new modal and translations)
• How can QA verify? (Through UI, API, AdminApp or AdminAdminApp?)
  • Through UI, together with the RDM-wiki-develop PR:
    1. Edit a wiki page, make unsaved changes, click Close → modal appears
    2. Cancel keeps the editor open
    3. Discard / Save and Close closes as expected
    4. Japanese locale shows the translated strings
• If verifying through API, what's the new version? Please include the endpoints in PR notes or Dev docs.
  • N/A
• What features or workflows might this change impact?
  • Wiki edit page close flow
• How will this impact performance?
  • Negligible

Documentation

• No documentation updates required

Side Effects

• None expected from this PR alone. Full behavior requires the companion RDM-wiki-develop change.

Ticket

https://redmine.devops.rcos.nii.ac.jp/issues/61563