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.

QUICKSTART.md

@@ -0,0 +1,231 @@
+# Quick Start Guide
+
+## Project Setup (5 minutes)
+
+### 1. Open in VS Code
+
+```bash
+# Option A: Open the workspace file directly
+code webdrop_bridge.code-workspace
+
+# Option B: Open the folder
+code .
+```
+
+### 2. Install Dependencies
+
+```bash
+# Create virtual environment
+python -m venv venv
+
+# Activate virtual environment
+source venv/bin/activate    # macOS/Linux
+# venv\Scripts\activate     # Windows
+
+# Install development dependencies
+pip install -r requirements-dev.txt
+```
+
+### 3. Verify Installation
+
+```bash
+# Run project structure tests
+pytest tests/unit/test_project_structure.py -v
+
+# Expected output:
+# test_project_structure.py::test_project_structure PASSED
+# test_project_structure.py::test_essential_files PASSED
+# test_project_structure.py::test_python_package_structure PASSED
+```
+
+## Project Structure Overview
+
+```
+webdrop-bridge/
+│
+├── src/webdrop_bridge/          ← Main application code
+│   ├── core/                    ← Business logic (validator, drag interceptor)
+│   ├── ui/                      ← UI components (main window, widgets)
+│   └── utils/                   ← Utilities (logging, helpers)
+│
+├── tests/                       ← Test suite
+│   ├── unit/                    ← Unit tests
+│   ├── integration/             ← Integration tests
+│   └── fixtures/                ← Test data
+│
+├── build/                       ← Build automation
+│   ├── windows/                 ← Windows-specific
+│   ├── macos/                   ← macOS-specific
+│   └── scripts/                 ← Build scripts
+│
+├── docs/                        ← Documentation
+│   └── ARCHITECTURE.md          ← Architecture guide
+│
+├── webapp/                      ← Embedded web application
+│   └── index.html               ← Test drag-drop page
+│
+├── DEVELOPMENT_PLAN.md          ← Detailed roadmap
+├── README.md                    ← User documentation
+├── CONTRIBUTING.md              ← Contributing guidelines
+└── Makefile                     ← Convenience commands
+```
+
+## Development Workflow
+
+### Phase 1: Core Components (Now)
+
+The project is structured to begin implementing core components. Start with:
+
+1. **Configuration System** (`src/webdrop_bridge/config.py`)
+   - Environment-based configuration
+   - Validation and defaults
+
+2. **Path Validator** (`src/webdrop_bridge/core/validator.py`)
+   - Whitelist-based path validation
+   - Security checks
+
+3. **Drag Interceptor** (`src/webdrop_bridge/core/drag_interceptor.py`)
+   - Qt drag-and-drop handling
+   - Text-to-file conversion
+
+4. **Main Window** (`src/webdrop_bridge/ui/main_window.py`)
+   - Qt application window
+   - WebEngine integration
+
+See [DEVELOPMENT_PLAN.md](DEVELOPMENT_PLAN.md#phase-1-foundation-weeks-1-4) for detailed specifications.
+
+## Common Tasks
+
+### Running Tests
+
+```bash
+# All tests
+pytest tests -v
+
+# With coverage
+pytest --cov=src/webdrop_bridge
+
+# Specific test type
+pytest tests/unit/ -v           # Unit tests
+pytest tests/integration/ -v    # Integration tests
+```
+
+### Code Quality
+
+```bash
+# Format code
+tox -e format
+
+# Check formatting
+tox -e lint
+
+# Type checking
+tox -e type
+
+# All checks at once
+tox
+```
+
+### Building
+
+```bash
+# Windows MSI
+python build/scripts/build_windows.py
+
+# macOS DMG
+bash build/scripts/build_macos.sh
+```
+
+### Documentation
+
+```bash
+# Build Sphinx docs
+tox -e docs
+
+# View docs
+open docs/_build/html/index.html  # macOS
+start docs\_build\html\index.html # Windows
+```
+
+## Using Makefile (Convenience)
+
+```bash
+# List all commands
+make help
+
+# Install dependencies
+make install-dev
+
+# Run tests
+make test
+
+# Code quality
+make lint
+make format
+make type
+
+# Build
+make build-windows
+make build-macos
+
+# Clean
+make clean
+```
+
+## VS Code Tips
+
+### Debugging
+
+1. **Set breakpoint**: Click line number
+2. **Start debugging**: F5 (or Run → Run Without Debugging)
+3. **Step over**: F10
+4. **Step into**: F11
+
+Configurations available in `.vscode/launch.json`:
+- Python: Current File
+- WebDrop Bridge (main application)
+
+### Testing in VS Code
+
+1. **Open test file**: `tests/unit/test_project_structure.py`
+2. **Run test**: Click "Run Test" above test function
+3. **Debug test**: Click "Debug Test"
+
+### Recommended Extensions
+
+- Python (ms-python.python)
+- Pylance (ms-python.vscode-pylance)
+- Black Formatter (ms-python.black-formatter)
+- Ruff (charliermarsh.ruff)
+
+## Configuration
+
+Create `.env` file from template:
+
+```bash
+cp .env.example .env
+```
+
+Edit as needed:
+- `WEBAPP_URL` - Web app location
+- `ALLOWED_ROOTS` - Whitelisted directories
+- `LOG_LEVEL` - DEBUG, INFO, WARNING, ERROR
+
+## Next Steps
+
+1. **Read** [DEVELOPMENT_PLAN.md](DEVELOPMENT_PLAN.md) for detailed roadmap
+2. **Review** [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md) for design decisions
+3. **Start** with Phase 1 core components
+4. **Write tests** for new code (TDD approach)
+5. **Follow** guidelines in [CONTRIBUTING.md](CONTRIBUTING.md)
+
+## Getting Help
+
+- 📖 **Documentation**: See README.md, DEVELOPMENT_PLAN.md, docs/
+- 🐛 **Issues**: GitHub Issues tracker
+- 💬 **Questions**: GitHub Discussions
+- 🤝 **Contributing**: See CONTRIBUTING.md
+
+---
+
+**Ready to start?** → Open `DEVELOPMENT_PLAN.md` Phase 1 section