feat: Implement GUI for SPED Automático with configuration management and theme support

- Added a new GUI application using the Iced library for user interaction.
- Implemented configuration loading from an INI file, including fields for model file, spreadsheet path, and reporting month.
- Introduced theme management with options for auto, light, and dark modes based on system preferences.
- Added functionality to browse for model and spreadsheet files.
- Implemented validation and formatting for the reporting month input.
- Integrated asynchronous processing of the SPED generation logic, with user feedback during execution.
- Created a logging mechanism to track application events and errors.
- Added tests for core functionalities including file reading/writing and data processing.

.gitignore

@@ -0,0 +1,9 @@
+target
+*.txt
+*.csv
+*.xlsx
+.DS_Store
+relatorio.csv
+sped_gui.log
+config.ini
+RELATORIO_SPED.xlsx