Remove legacy dead code: pre-LVGL screens and unused stubs

Delete 24 files (2487 lines):
- 18 legacy screen files (BootScreen, HomeScreen, NodesScreen,
  MessagesScreen, MessageView, SettingsScreen, HelpOverlay,
  NameInputScreen, MapScreen) replaced by Lv-prefixed LVGL versions
- PowerManager (superseded by hal/Power)
- hal/Audio (ES7210 stub, working audio is audio/AudioNotify)
- hal/GPS (stub, GPS deprioritized)

Move shared types (SettingType, SettingItem, SettingsCategory) from
deleted SettingsScreen.h into LvSettingsScreen.h.

Clean main.cpp: remove legacy includes, instances, and tab mapping.

Note: StatusBar and TabBar retained — still used by UIManager/main.cpp.

src/main.cpp

@@ -21,15 +21,6 @@
 #include "ui/UIManager.h"
 #include "ui/LvTabBar.h"
 #include "ui/LvInput.h"
-#include "ui/screens/BootScreen.h"
-#include "ui/screens/HomeScreen.h"
-#include "ui/screens/NodesScreen.h"
-#include "ui/screens/MessagesScreen.h"
-#include "ui/screens/MessageView.h"
-#include "ui/screens/SettingsScreen.h"
-#include "ui/screens/HelpOverlay.h"
-// MapScreen removed
-#include "ui/screens/NameInputScreen.h"
 #include "ui/screens/LvBootScreen.h"
 #include "ui/screens/LvHomeScreen.h"
 #include "ui/screens/LvNodesScreen.h"
@@ -98,17 +89,6 @@ Power powerMgr;
 AudioNotify audio;
 IdentityManager identityMgr;
 
-// --- Legacy Screens (kept for fallback during migration) ---
-BootScreen bootScreen;
-HomeScreen homeScreen;
-NodesScreen nodesScreen;
-MessagesScreen messagesScreen;
-MessageView messageView;
-SettingsScreen settingsScreen;
-HelpOverlay helpOverlay;
-// MapScreen removed
-NameInputScreen nameInputScreen;
-
 // --- LVGL Screens ---
 LvBootScreen lvBootScreen;
 LvHomeScreen lvHomeScreen;
@@ -124,9 +104,6 @@ LvNameInputScreen lvNameInputScreen;
 // Tab-screen mapping (4 tabs) — LVGL versions
 LvScreen* lvTabScreens[LvTabBar::TAB_COUNT] = {};
 
-// Legacy tab mapping (kept for reference)
-Screen* tabScreens[LvTabBar::TAB_COUNT] = {};
-
 // --- State ---
 bool radioOnline = false;
 bool bootComplete = false;