Mixed proposal format — lump sum for some trades, detailed for others in one proposal

Allow mixing lump sum and detailed line-item formats within a single proposal, on a per-trade basis. For example: show plumbing as a lump sum total, but show carpentry with full line-item detail — all in the same client-facing proposal document.

Currently proposals are either all detailed or all lump sum. Contractors need flexibility to hide detail on trades they sub out while showing detail on trades they self-perform.