The share management endpoints serialized the storage struct directly, returning
the bcrypt password_hash (crackable offline) and the bypass token for every
share an authenticated caller could list, with admins seeing them for all users.
Return a response DTO that exposes only whether a share is password-protected
(hasPassword) and drops both secrets. The storage struct keeps its tags so the
secrets stay persisted and the server-side auth/public flows are unchanged.
Updates the frontend to use hasPassword and adds a regression test.
