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.

tox.ini

@@ -0,0 +1,53 @@
+[tox]
+envlist = py{310,311,312},lint,type,docs
+skip_missing_interpreters = true
+
+[testenv]
+description = Run unit tests
+deps = -r{toxinidir}/requirements-dev.txt
+commands = pytest {posargs}
+
+[testenv:lint]
+description = Run linting checks (black, ruff, isort)
+skip_install = false
+commands =
+    black --check src tests
+    isort --check-only src tests
+    ruff check src tests
+
+[testenv:format]
+description = Auto-format code (black, isort)
+skip_install = false
+commands =
+    black src tests
+    isort src tests
+
+[testenv:type]
+description = Run type checking with mypy
+commands = mypy src/webdrop_bridge
+
+[testenv:docs]
+description = Build Sphinx documentation
+changedir = docs
+commands = sphinx-build -W -b html -d {envtmpdir}/doctrees . {envtmpdir}/html
+
+[testenv:coverage]
+description = Run tests with coverage report
+commands = pytest --cov=src/webdrop_bridge --cov-report=term-missing --cov-report=html
+
+[testenv:build-windows]
+description = Build Windows installer (MSI)
+platform = win32
+whitelist_externals = 
+    bash
+    powershell
+commands = 
+    python build/scripts/build_windows.py
+
+[testenv:build-macos]
+description = Build macOS DMG package
+platform = darwin
+whitelist_externals = 
+    bash
+commands = 
+    bash build/scripts/build_macos.sh