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>

README.md

@@ -2,7 +2,7 @@
 
 MCP server for [Family Wall](https://www.familywall.com) -- read and manage your family's circles, lists, and tasks directly from Claude.
 
-## Features (v0.4.10)
+## Features (v0.4.11)
 
 ### Read
 
@@ -10,7 +10,7 @@ MCP server for [Family Wall](https://www.familywall.com) -- read and manage your
 - `get_members` -- list members of a circle (or all circles)
 - `get_lists` -- list all task lists (optionally filtered by circle)
 - `get_tasks` -- list tasks in a specific list (includes `category_id` field)
-- `get_categories` -- list categories available for a list (locale-filtered, default: German)
+- `get_categories` -- list categories for a list (locale-filtered; `custom` flag marks user-created ones)
 - `get_activities` -- list recent wall activities (author resolved to display name)
 
 ### Write (with confirmation prompt)
@@ -19,7 +19,9 @@ MCP server for [Family Wall](https://www.familywall.com) -- read and manage your
 - `update_task` -- update text, description, and/or category of an existing task
 - `toggle_task` -- mark a task complete or reopen it
 - `delete_task` -- permanently delete a task
-- `like_post` -- like or unlike a wall post/activity
+- `create_category` -- create a custom category for a shopping list (with optional icon)
+- `delete_category` -- delete a custom category (system categories are protected)
+- `like_post` -- like a wall post/activity
 
 ## Requirements