Custom work areas now fully support dimensions and estimates

Set proper dimensions and add line items to STRUCTURE, SITE, and ELEVATION work areas — formulas now resolve correctly.

Bug Fixes

STRUCTURE, SITE, and ELEVATION work areas were asking users to manually enter area values when those should be calculated from dimensions, and their measurements lived in a separate JSON structure instead of linked columns — which meant formulas (floor area, perimeter, volume) returned zero instead of actual values.

Now all five work area types (ROOM, STRUCTURE, SITE, ELEVATION, ROOF) share the same column-backed dimension model. Users enter length, width, and height in feet and inches, and the UI displays computed tiles (Floor Area + Volume for STRUCTURE, Area for SITE, Wall Area for ELEVATION). Non-ROOM work areas now appear as groups in the manual estimate table so you can add and edit line items directly.