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>

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Marcus van Elst
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.