Restructured the Site Assessment data model end-to-end — retired deprecated fields and introduced new ones for construction status and mounting configuration, engineered so legacy production records remain fully readable and writable with zero data migration. Traced and updated all downstream business logic dependent on the removed fields — including the quotation approval pipeline — ensuring approvals no longer rely on retired data. Reworked the Site Assessment screen (~200 lines of logic) around the new model, and solved a backward-compatibility problem by building a normalization layer that reconciles inconsistent legacy roof-type values with the new option set, including a new combined selection.