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.

tests/unit/__init__.py

@@ -0,0 +1 @@
+"""Unit tests initialization."""

tests/unit/test_project_structure.py

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+"""Minimal test to verify project structure."""
+from pathlib import Path
+
+import pytest
+
+
+def test_project_structure():
+    """Verify essential project directories exist."""
+    root = Path(__file__).parent.parent.parent
+    
+    essential_dirs = [
+        "src/webdrop_bridge",
+        "tests/unit",
+        "tests/integration",
+        "build/scripts",
+        "docs",
+        "webapp",
+    ]
+    
+    for dir_path in essential_dirs:
+        full_path = root / dir_path
+        assert full_path.exists(), f"Missing directory: {dir_path}"
+        assert full_path.is_dir(), f"Not a directory: {dir_path}"
+
+
+def test_essential_files():
+    """Verify essential configuration files exist."""
+    root = Path(__file__).parent.parent.parent
+    
+    essential_files = [
+        "pyproject.toml",
+        "setup.py",
+        "pytest.ini",
+        "tox.ini",
+        ".env.example",
+        "README.md",
+        "DEVELOPMENT_PLAN.md",
+        "LICENSE",
+    ]
+    
+    for file_path in essential_files:
+        full_path = root / file_path
+        assert full_path.exists(), f"Missing file: {file_path}"
+        assert full_path.is_file(), f"Not a file: {file_path}"
+
+
+def test_python_package_structure():
+    """Verify Python package __init__ files exist."""
+    root = Path(__file__).parent.parent.parent
+    
+    packages = [
+        "src/webdrop_bridge",
+        "src/webdrop_bridge/core",
+        "src/webdrop_bridge/ui",
+        "src/webdrop_bridge/utils",
+        "tests",
+    ]
+    
+    for pkg_path in packages:
+        init_file = root / pkg_path / "__init__.py"
+        assert init_file.exists(), f"Missing __init__.py in {pkg_path}"
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])