feat(frontend): esqueleto CommonUI de MainMenu (boot→login→lobby)

Estrutura principal de front-end estilo Lyra portada para C++ proprio do
ZMMO (sem CommonGame), seguindo o padrao C++ Abstract -> WBP concreto:

- EZMMOFrontEndState / EZMMOLobbyPage e GameplayTags UI.Layer.* nativos
- UUIActivatableScreen_Base: base de tela (input config, hook de tema,
  voltar) espelhando o padrao de UUIButton_Base
- UUIPrimaryGameLayout_Base: switch principal (4 stacks CommonUI/camada)
- UUIManagerSubsystem (LocalPlayer): dono do root layout, idempotente
- UUIFrontEndFlowSubsystem (GameInstance): maquina de estados + driver
  de rede (Boot->Connecting->Login->ServerSelect->Lobby->EnteringWorld
  ->InWorld); Lobby e o hub logado, paginas internas = EZMMOLobbyPage
- UUIFrontEndScreenSet (DataAsset): mapa estado->tela, forge-ready
- AZMMOFrontEndGameMode + AZMMOFrontEndPlayerController
- GameInstance: bAutoConnectOnStart=false (conexao dirigida pelo fluxo)
- Build.cs: +GameplayTags; ARQUITETURA.md PR-first (s2.1/2.2/3.3/4.8/5)
- Assets: L_FrontEnd (GameMode via World Settings), WBP_PrimaryGameLayout,
  DA_FrontEndScreenSet; Config wiring

WBPs de pagina (Boot/Login/...) virao do Zeus UMG Forge depois (s4.8).
Smoke test PIE OK: root layout no viewport, fluxo Boot->Connecting,
no-op+log para telas nao configuradas, sem crash.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Config/DefaultGame.ini

@@ -24,3 +24,8 @@ ProjectName=Third Person Game Template
 ;CalendarTable=/Game/ZMMO/UI/Themes/DT_ThemeCalendar.DT_ThemeCalendar
 UIStyleTable=/Game/ZMMO/Data/UI/DT_UI_Styles.DT_UI_Styles
 ;DevThemeOverride=Christmas
+
+[/Script/ZMMO.UIFrontEndFlowSubsystem]
+; Mapa estado->tela. O DA já existe (RootLayoutClass = WBP_PrimaryGameLayout);
+; StateScreens fica vazio até os WBPs de página virem do Zeus UMG Forge (§4.8).
+ScreenSetAsset=/Game/ZMMO/UI/FrontEnd/DA_FrontEndScreenSet.DA_FrontEndScreenSet