feat: add ad management ui

[soonduck-dreams]

Summary

• implement admin ad management controller, client, and view models covering ads, slots, placements, and presigned uploads
• add Thymeleaf pages, sidebar navigation, and JavaScript to manage ads, slots, and schedules with viewer/editor role handling
• expand current admin profile/client to expose role codes for feature access control

Testing

• ./gradlew clean build --console=plain

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Codex Task