chore: finalize v1.0.0 — cleanup, unified errors, date validation

- Move integration tests to tests/; fix .gitignore to scope root-only
- Remove tracked debug artefacts (probe2_stderr/stdout.txt)
- __init__.py: version via importlib.metadata; export create_server in __all__
- server.py: unified JSON error format {"error":"..."} for all tools
- server.py: date validation (YYYY-MM-DD) for all meal-plan tools
- server.py: clear_list reports partial failures (failed_count, failed_ids)
- server.py: -> str annotations on get_circles, get_tasks, get_activities
- server.py: document TODO:94 as known limitation (no name in sortingIndexByTaskList)
- server.py: date validation also added to get_meal_plan
- Add LICENSE (MIT, Marcus van Elst)
- Add CHANGELOG.md (Keep a Changelog, v0.1.0–v1.0.0)
- README.md: restructured by use case; 🔒 marks write tools
- CLAUDE.md: update to v1.0.0 state; condense roadmap history
- SPEC.md: add version stamp
- pyproject.toml: version 1.0.0 (single source of truth)

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

SPEC.md

@@ -3,6 +3,8 @@
 Erarbeitet durch Browser-Traffic-Analyse und React-Fiber-Analyse (April 2026).
 Es gibt keine offizielle API-Dokumentation.
 
+**Stand: v1.0.0 (2026-04-17)**
+
 ## Base URL
 https://api.familywall.com/api