Performs a comprehensive project rename from 'barcode_scanner' to 'e_scan' (or 'eScan' for user-facing labels). This update spans all relevant files, including:
- Application IDs and bundle identifiers for Android, iOS, macOS, and Linux.
- VS Code launch configurations.
- Dart package import paths.
- Project names and titles in `pubspec.yaml`, `README.md`, and platform-specific configurations (e.g., CMakeLists, Info.plist, AndroidManifest).
Renames `AuthStruct` to `AuthModel` and `ProductStruct` to `ProductModel` to align with a consistent data model naming convention.
Updates all relevant imports, type declarations, and method signatures across the application to reflect these changes, improving codebase clarity and maintainability.
Includes minor code style improvements and refactorings in other components.
