admin-ui: station image has no upload UI — the owner's face-of-the-station is curl-only

[genwave-radio]

T307 shipped PUT/DELETE /api/station/image and every consumer slot (F131), but no admin surface drives it — STORY-339's station owner can't do it from the console. The T308 wire's 'upload' step was a curl. Needs a Settings-or-Wardrobe-adjacent control using the existing honest ProblemDetails mapping (ImageNormalizeProblemMapper). Project: Admin UI (#5).