Fix game object sign orientation and restrict nameplates to target only

Game object M2 models share the same default facing (+renderX) as
character models, so apply the same π/2 offset instead of π when
computing renderYawM2go from canonical yaw. This corrects street signs
and hanging shop signs that were 90° off after the server-yaw formula
fix.

Nameplates (health bar + name label) are now only rendered for the
currently targeted entity, matching WoW's default UI behaviour and
reducing visual noise.

src/core/application.cpp

@@ -6698,7 +6698,9 @@ void Application::spawnOnlineGameObject(uint64_t guid, uint32_t entry, uint32_t
 
     glm::vec3 renderPos = core::coords::canonicalToRender(glm::vec3(x, y, z));
     const float renderYawWmo = orientation;
-    const float renderYawM2go = orientation + glm::radians(180.0f);
+    // M2 game objects: model default faces +renderX. renderYaw = canonical + 90° = server_yaw
+    // (same offset as creature/character renderer so all M2 models face consistently)
+    const float renderYawM2go = orientation + glm::radians(90.0f);
 
     bool loadedAsWmo = false;
     if (isWmo) {

src/ui/game_screen.cpp

@@ -4718,6 +4718,9 @@ void GameScreen::renderNameplates(game::GameHandler& gameHandler) {
         auto* unit = dynamic_cast<game::Unit*>(entityPtr.get());
         if (!unit || unit->getMaxHealth() == 0) continue;
 
+        // Only show nameplate for the currently targeted unit
+        if (guid != targetGuid) continue;
+
         // Convert canonical WoW position → render space, raise to head height
         glm::vec3 renderPos = core::coords::canonicalToRender(
             glm::vec3(unit->getX(), unit->getY(), unit->getZ()));