Improve UI layout, spell casting, and realm selection screen

- Fix action bar, bag bar, chat window to track window resize (Always pos)
- Show spell names in cast bar instead of spell IDs
- Play precast/cast-complete sounds via SpellSoundManager
- Fix hearthstone to use CMSG_CAST_SPELL directly (avoids slot sync issues)
- Show map name instead of coordinates in hearthstone tooltip
- Show cooldown time remaining in action bar tooltips
- Search equipped slots and bags for action bar item icons
- Redesign realm screen: back button, larger table/buttons, auto-select
  realm with characters, double-click to enter, proportional columns

src/core/application.cpp

@@ -961,6 +961,15 @@ void Application::setupUICallbacks() {
         }
     });
 
+    // Realm screen back button - return to login
+    uiManager->getRealmScreen().setOnBack([this]() {
+        if (authHandler) {
+            authHandler->disconnect();
+        }
+        uiManager->getRealmScreen().reset();
+        setState(AppState::AUTHENTICATION);
+    });
+
     // Character selection callback
     uiManager->getCharacterScreen().setOnCharacterSelected([this](uint64_t characterGuid) {
         LOG_INFO("Character selected: GUID=0x", std::hex, characterGuid, std::dec);