Add initial project structure and documentation

- Created architecture documentation outlining high-level design, module organization, data flow, security model, performance considerations, testing strategy, and deployment architecture.
- Added pyproject.toml for project metadata and dependencies management.
- Introduced requirements files for development and production dependencies.
- Set up testing configuration with pytest and tox.
- Established basic directory structure for source code and tests, including __init__.py files.
- Implemented a sample web application (index.html) for drag-and-drop functionality.
- Configured VS Code workspace settings for Python development.

requirements-dev.txt

@@ -0,0 +1,19 @@
+-r requirements.txt
+
+# Testing
+pytest>=7.4.0
+pytest-cov>=4.1.0
+pytest-qt>=4.2.0
+
+# Code Quality
+black>=23.0.0
+ruff>=0.1.0
+mypy>=1.5.0
+isort>=5.12.0
+
+# Building
+pyinstaller>=6.0.0
+
+# Documentation
+sphinx>=7.0.0
+sphinx-rtd-theme>=1.3.0