feat: versioning sémantique (single source of truth)

- Crée src/__version__.py comme source unique de version (2.1.0)
- pyproject.toml utilise dynamic version via setuptools attr
- Affiche la version dans le footer de la sidebar (base.html)
- Ajoute endpoint /health avec version et status

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.backends._legacy:_Backend"
 
 [project]
 name = "t2a"
-version = "2.0.0"
+dynamic = ["version"]
 description = "Pipeline de codage CIM-10/CCAM automatise pour le PMSI hospitalier"
 readme = "README.md"
 requires-python = ">=3.11"
@@ -43,6 +43,9 @@ dev = [
 [project.scripts]
 t2a = "src.main:main"
 
+[tool.setuptools.dynamic]
+version = {attr = "src.__version__.__version__"}
+
 [tool.setuptools.packages.find]
 include = ["src*"]