feat: due_date, assignee_ids, list_id for create_task/update_task (v0.4.14)

- create_task: new optional params due_date (ISO 8601) and assignee_ids (list[str])
- update_task: new optional params due_date, assignee_ids, and list_id (move task)
- get_tasks: returns due_date and assignee_ids fields per task
- API params verified via FW_DEBUG=1: dueDate, assignee, taskListId
- SPEC.md, README, CLAUDE.md updated

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

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "mcp-familywall"
-version = "0.4.13"
+version = "0.4.14"
 description = "MCP server for Family Wall — read your family's lists and tasks via Claude"
 readme = "README.md"
 requires-python = ">=3.12"