Simplifile - json complete rewrite

Subgoal 1: Centralized Data Model

Created unified SimplifilePackage, SimplifileDocument, Party, LegalDescription, and ReferenceInformation classes
Implemented consistent to_api_dict() and to_display_dict() methods for each model
Ensured consistent representation of data across the application

Subgoal 2: Remove Default Values

Removed hardcoded default values like "OCEAN CLUB VACATIONS LLC"
Added validation to ensure required fields come from Excel data
Kept only "KING CUNNINGHAM LLC TR" as the single static value for Deed documents

Subgoal 3: Update UI to Match Models

Updated BatchPreviewDialog to use the new models
Fixed grantor handling in document previews
Ensured appropriate validation in the UI
Made the UI reflect the actual data that will be sent to the API