Feat: add export functionality with GUI for data and graphs

- Implemented ExportWindow class for exporting data and graphs in various formats (JSON, XML, PDF).
- Integrated ExportManager to handle export logic.
- Added export option in the main application menu.
- Enhanced user interface with data summary and export options.
- Included error handling and success messages for export operations.
- Updated dependencies in the lock file to include reportlab and lxml for PDF generation.

pyproject.toml

@@ -1,14 +1,16 @@
 [project]
 name = "thechart"
-version = "1.7.5"
+version = "1.8.5"
 description = "Chart to monitor your medication intake over time."
 readme = "README.md"
 requires-python = ">=3.13"
 dependencies = [
     "colorlog>=6.9.0",
     "dotenv>=0.9.9",
+    "lxml>=6.0.0",
     "matplotlib>=3.10.3",
     "pandas>=2.3.1",
+    "reportlab>=4.4.3",
     "tk>=0.1.0",
 ]