feat: create_category + delete_category tools (v0.4.11)

Verified via systematic FW_DEBUG=1 probing:
- taskcategoryput: requires 'name'; optional 'emoji' (Unicode or string code)
  accepted as-is. 'listId' param has no per-list effect — categories are
  family-wide.
- taskcategorydelete: uses 'id' param (not 'metaId'), returns r='true'.

Changes:
- create_category(list_id, name, icon=None): creates custom category via
  taskcategoryput; icon maps to 'emoji' API param
- delete_category(category_id): safety check via accgetallfamily looks up
  rights.canDelete='true'; system categories (rights.canDelete=null) are
  refused with a clear error
- get_categories: now exposes 'custom' bool field (rights.canDelete='true')
  so callers can identify deletable categories
- SPEC.md: document taskcategoryput + taskcategorydelete params, responses,
  error formats, and system-category protection behaviour

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 = "0.4.10"
+version = "0.4.11"
 description = "MCP server for Family Wall — read your family's lists and tasks via Claude"
 readme = "README.md"
 requires-python = ">=3.12"