docs(M7): aligner guide, TODO et pre-commit pour la sync CalDAV

Met à jour la documentation et la configuration pour le jalon M7 selon
les décisions d'architecture :

- GUIDE_DEV_PYTHON.md §7 : API réelle caldav>=1.3.0 (pas le pseudo-code),
  calendar_path (pas calendar_name), plan CalDAVSyncPlan explicite avant
  exécution, pas d'état local (scan distant), événements non marqués
  jamais modifiés
- TODO.md M7 : suppression de sync/state.py et BlogRSSState, ajout de
  l'exécution du plan et de la protection des événements non gérés
- .pre-commit-config.yaml : caldav>=1.3.0 ajouté aux additional_dependencies
  du hook mypy

Co-authored-by: opencode/coder <coder@agents.invalid>
Co-authored-by: opencode/tech-writer <tech-writer@agents.invalid>

.pre-commit-config.yaml

@@ -26,7 +26,7 @@ repos:
         name: mypy
         entry: mypy
         language: python
-        additional_dependencies: ["mypy>=1.10.0", "pydantic>=2.0.0", "pydantic-settings>=2.0.0", "pytest>=8.0.0", "types-requests>=2.31.0", "icalendar>=5.0.0", "pronotepy>=2.15.0", "responses>=0.25.0", "pytest-mock>=3.10.0", "feedparser>=6.0.0"]
+        additional_dependencies: ["mypy>=1.10.0", "pydantic>=2.0.0", "pydantic-settings>=2.0.0", "pytest>=8.0.0", "types-requests>=2.31.0", "icalendar>=5.0.0", "pronotepy>=2.15.0", "responses>=0.25.0", "pytest-mock>=3.10.0", "feedparser>=6.0.0", "caldav>=1.3.0"]
         types: [python]
         pass_filenames: true