test(recipe): cover null serves/cookTimeMin and capitalised effort rejection

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/test/java/com/recipeapp/recipe/RecipeControllerTest.java

@@ -161,6 +161,19 @@ class RecipeControllerTest {
         verify(recipeService).deleteRecipe(HOUSEHOLD_ID, RECIPE_ID);
     }
 
+    @Test
+    void createRecipeWithCapitalisedEffortShouldReturn400() throws Exception {
+        var body = """
+                {"name":"Test","effort":"Easy","tagIds":["%s"],"ingredients":[{"quantity":1,"unit":"g","newIngredientName":"x","sortOrder":0}]}
+                """.formatted(UUID.randomUUID());
+
+        mockMvc.perform(post("/v1/recipes")
+                        .principal(() -> "sarah@example.com")
+                        .contentType(org.springframework.http.MediaType.APPLICATION_JSON)
+                        .content(body))
+                .andExpect(status().isBadRequest());
+    }
+
     private RecipeCreateRequest sampleCreateRequest() {
         var ingredientId = UUID.randomUUID();
         return new RecipeCreateRequest(