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/modules/recipes.py

@@ -160,7 +160,9 @@ def build_create_params(
     if url is not None:
         params["recipe.url"] = url
     if category_ids is not None:
-        params["recipe.recipeCategoryIdList"] = category_ids
+        # For create: empty list just means no categories (don't send parameter).
+        if len(category_ids) > 0:
+            params["recipe.recipeCategoryIdList"] = category_ids
     return params
 
 
@@ -225,5 +227,11 @@ def build_update_params(
     if url is not None:
         params["recipe.url"] = url
     if category_ids is not None:
-        params["recipe.recipeCategoryIdList"] = category_ids
+        # Empty list: send empty string to remove all categories.
+        # Non-empty list: send as-is (httpx sends list values multiple times).
+        # Verified via testing: empty string "" removes categories, empty list [] does not.
+        if len(category_ids) == 0:
+            params["recipe.recipeCategoryIdList"] = ""
+        else:
+            params["recipe.recipeCategoryIdList"] = category_ids
     return params