Add Sprint#board_name

Use `Sprint#board_name` in `RbTaskboardsController` instead of
building the board name inline.

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

Author: myabc

modules/backlogs/app/controllers/rb_taskboards_controller.rb

@@ -40,8 +40,7 @@ def show
   private
 
   def load_or_create_board
-    name   = "#{@project.name}: #{@sprint.name}"
-    result = TaskBoards::CreateService.ensure(user: current_user, project: @project, name:)
+    result = TaskBoards::CreateService.ensure(user: current_user, project: @project, name: @sprint.board_name)
 
     if result.success?
       @board = result.result

modules/backlogs/app/models/sprint.rb

@@ -160,6 +160,10 @@ def settings(project)
     version_settings.find { it.project_id == project.id || it.project_id.nil? }
   end
 
+  def board_name
+    "#{project.name}: #{name}"
+  end
+
   private
 
   def create_wiki_page(page_title, author: User.current)

modules/backlogs/spec/models/sprint_spec.rb

@@ -261,6 +261,13 @@
     end
   end
 
+  describe "#board_name" do
+    it "returns project name and sprint name separated by a colon" do
+      sprint = build_stubbed(:sprint, name: "Sprint 1", project: build_stubbed(:project, name: "My Project"))
+      expect(sprint.board_name).to eq("My Project: Sprint 1")
+    end
+  end
+
   describe "#wiki_page" do
     let(:wiki) { create :wiki, project: }
     let(:wiki_page) { WikiPage.where(wiki:, title: sprint.wiki_page).first }