fix(recipes): two bugs in recipe categories (v0.8.1)

Bug 1: update_recipe(category_ids=[]) didn't remove categories
- Fixed: send empty string "" to API to remove all categories
- Non-empty lists continue to work as expected
- Verified via FW_DEBUG=1 testing

Bug 2: get_recipe_categories() only showed used categories
- Fixed: always return 5 free-tier standard categories
- Added _get_family_id() helper to extract family ID
- Now returns all available category IDs even on new accounts
- Standard categories: category/<familyId>_2 through _6

Version: 0.8.0 → 0.8.1
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/mcp_familywall/__init__.py

@@ -1 +1 @@
-__version__ = "0.8.0"
+__version__ = "0.8.1"