migrate to pyproject.toml following PEP 621 standard

Replace requirements.txt with modern pyproject.toml configuration to align with Python packaging best practices. All dependencies are now declared in [project] section, with optional dev dependencies (ruff, mypy) in [project.optional-dependencies].

Updated all references:
- Dockerfile: Install with `pip install .` instead of `-r requirements.txt`
- setup_env.sh: Install with `pip install -e .` for editable development mode
- README.md: Updated installation instructions in both quick start and development sections
- CLAUDE.md: Updated documentation references
- .gitignore: Added common IDE and tool directories

Installation is now: `pip install -e .` for development or `pip install .` for production.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -45,7 +45,7 @@ source env/bin/activate && python main.py --dump
 The application requires:
 - Python 3.10+
 - Virtual environment at `env/` (must be activated before running commands)
-- Dependencies from `requirements.txt` (includes FastAPI, uvicorn, Socket.IO)
+- Dependencies from `pyproject.toml` (includes FastAPI, uvicorn, Socket.IO)
 
 Docker deployment:
 ```bash
@@ -278,7 +278,7 @@ The application uses a web-based interface accessible via browser:
 
 **Dockerfile:**
 - Based on `python:3.11-slim`
-- Installs dependencies from `requirements.txt`
+- Installs dependencies from `pyproject.toml`
 - Exposes port 8080
 - Health check on `/api/status`