feat: add delete_circle tool (v0.7.2)

Implements `delete_circle(circle_id)` using the verified `adminwipefamily`
endpoint. Protects the primary circle via `isFirstFamily` check. Probe
circles family/23447370 and family/23447378 cleaned up during testing.

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, tasks, and recipes directly from Claude.
 
-## Features (v0.7.1)
+## Features (v0.7.2)
 
 ### Read
 
@@ -29,7 +29,8 @@ MCP server for [Family Wall](https://www.familywall.com) -- read and manage your
 - `create_recipe` -- create a new recipe (name, description, ingredients, instructions, prep/cook time, serves, url); use `\n` to separate ingredient lines
 - `update_recipe` -- update any field of an existing recipe (partial update — omitted fields unchanged)
 - `delete_recipe` -- permanently delete a recipe (only own recipes)
-- `create_circle` -- create a new Family Wall circle (group); note: circles cannot be deleted via API
+- `create_circle` -- create a new Family Wall circle (group)
+- `delete_circle` -- permanently delete a circle and all its content (primary circle is protected)
 - `add_member_to_circle` -- invite a person to a circle by e-mail (for new Family Wall users only; existing accounts require in-app invitation)
 
 ## Requirements