- Add a per-disposition info line under the Disposition dropdown so re-bill
vs pass-through vs company expense is clear in-context (en + de).
- Markup is a re-bill concept only: the control now renders solely for
rebill, and a pass-through always bills at cost. Enforced server-side too
(categorizeInbound applies markup only when disposition === 'rebill').
- Clarify "Book to" with a hint — it attributes the supplier cost to an
event in the tax report / ledger export, separate from who you re-bill to.