[codex] Add admin notification hooks

[Rabithua]

Summary

• Add administrator-only notification hooks under the notification settings group.
• Support Bark, HTTP POST, and admin PWA delivery channels for user registration and public note creation events.
• Add the admin Hooks tab with dialog-based channel creation/editing and localized zh/en/ja copy.

Notes

• Hook delivery is independent from user broadcast notifications.
• HTTP/Bark delivery blocks local/private network targets and does not echo endpoint response bodies in test results.
• Public note events fire on creation when the note is created as public; updates/private-to-public are not included.

Validation

• server: bun run lint
• server: bun run build
• web: bun run lint
• web: bun run build
• git diff --check

[chatgpt-codex-connector]

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