Added a new file, `FORM_APPLICATION_CONTEXT.md`, to the solution file `EnvelopeGenerator.sln`. This file provides detailed documentation of the legacy VB.NET Windows Forms application, including its architecture, workflows, and migration plan to the ReceiverUI + API architecture.
The documentation outlines the application's purpose, primary libraries, project structure, and key forms with their respective features and behaviors. It also describes data models, controllers, and their methods, along with technical details such as coordinate systems, status colors, and master-detail grid patterns.
Additionally, the file includes implementation notes for key features like drag-and-drop file uploads, auto-complete for receiver emails, and PDF merging. Workflow summaries and a data flow diagram are provided to clarify the application's processes. The document concludes with key takeaways to ensure consistency during the migration.
