Migration v1 (Flask) -> v2 (FastAPI + Vue.js) complétée

✨ Changements majeurs:
- Suppression complète du code Flask legacy
- Migration backend FastAPI vers racine /backend
- Migration frontend Vue.js vers racine /frontend
- Suppression de notytex-v2/ (code monté à la racine)

✅ Validations:
- Backend démarre correctement (port 8000)
- API /api/v2/health répond healthy
- 99/99 tests unitaires passent
- Frontend configuré avec proxy Vite

📝 Documentation:
- README.md réécrit pour v2
- Instructions de démarrage mises à jour
- .gitignore adapté pour backend/frontend/

🎯 Architecture finale:
notytex/
├── backend/     # FastAPI + SQLAlchemy + Pydantic
├── frontend/    # Vue 3 + Vite + TailwindCSS
├── docs/        # Documentation
└── school_management.db  # Base de données (inchangée)

Jalon 6 complété: Application v2 prête pour utilisation!

backend/pyproject.toml

@@ -0,0 +1,71 @@
+[project]
+name = "notytex-backend"
+version = "2.0.0"
+description = "Backend API FastAPI pour Notytex - Système de gestion scolaire"
+readme = "README.md"
+requires-python = ">=3.11"
+license = {text = "MIT"}
+authors = [
+    {name = "Notytex Team"}
+]
+
+dependencies = [
+    "fastapi>=0.109.0",
+    "uvicorn[standard]>=0.27.0",
+    "sqlalchemy>=2.0.25",
+    "aiosqlite>=0.19.0",
+    "pydantic>=2.5.0",
+    "pydantic-settings>=2.1.0",
+    "python-multipart>=0.0.6",
+    "python-dotenv>=1.0.0",
+    "httpx>=0.26.0",
+    "email-validator>=2.1.0",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=7.4.0",
+    "pytest-asyncio>=0.23.0",
+    "pytest-cov>=4.1.0",
+    "httpx>=0.26.0",
+    "black>=24.1.0",
+    "ruff>=0.1.0",
+    "mypy>=1.8.0",
+]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["api", "core", "domain", "infrastructure", "schemas"]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+testpaths = ["tests"]
+python_files = "test_*.py"
+python_functions = "test_*"
+addopts = "-v --tb=short"
+
+[tool.black]
+line-length = 88
+target-version = ['py311']
+
+[tool.ruff]
+line-length = 88
+target-version = "py311"
+select = [
+    "E",  # pycodestyle errors
+    "W",  # pycodestyle warnings
+    "F",  # pyflakes
+    "I",  # isort
+    "B",  # flake8-bugbear
+    "C4", # flake8-comprehensions
+]
+ignore = ["E501"]  # line too long (handled by black)
+
+[tool.mypy]
+python_version = "3.11"
+warn_return_any = true
+warn_unused_configs = true
+ignore_missing_imports = true