Implement NPC greeting voice lines

Added NPC voice manager that plays greeting sounds when clicking on NPCs:

Features:
- Voice line library with multiple race/gender voice types (Human, Dwarf,
  Night Elf, etc.)
- 3D positional audio - voice comes from NPC location
- Cooldown system prevents spam clicking same NPC
- Randomized pitch/volume for variety
- Loads greeting sounds from character voice files in MPQ
- Generic fallback voices for NPCs without specific voice types

Voice lines trigger automatically when gossip window opens (SMSG_GOSSIP_MESSAGE).
Uses same audio system as other sound effects with ma_sound_set_position.

src/core/application.cpp

@@ -6,6 +6,7 @@
 #include "core/logger.hpp"
 #include "core/memory_monitor.hpp"
 #include "rendering/renderer.hpp"
+#include "audio/npc_voice_manager.hpp"
 #include "rendering/camera.hpp"
 #include "rendering/camera_controller.hpp"
 #include "rendering/terrain_renderer.hpp"
@@ -814,6 +815,15 @@ void Application::setupUICallbacks() {
         }
     });
 
+    // NPC greeting callback - play voice line
+    gameHandler->setNpcGreetingCallback([this](uint64_t guid, const glm::vec3& position) {
+        if (renderer && renderer->getNpcVoiceManager()) {
+            // Convert canonical to render coords for 3D audio
+            glm::vec3 renderPos = core::coords::canonicalToRender(position);
+            renderer->getNpcVoiceManager()->playGreeting(guid, audio::VoiceType::GENERIC, renderPos);
+        }
+    });
+
     // "Create Character" button on character screen
     uiManager->getCharacterScreen().setOnCreateCharacter([this]() {
         uiManager->getCharacterCreateScreen().reset();

src/game/game_handler.cpp

@@ -4569,6 +4569,15 @@ void GameHandler::handleGossipMessage(network::Packet& packet) {
     if (questDetailsOpen) return; // Don't reopen gossip while viewing quest
     gossipWindowOpen = true;
     vendorWindowOpen = false; // Close vendor if gossip opens
+
+    // Play NPC greeting voice
+    if (npcGreetingCallback_ && currentGossip.npcGuid != 0) {
+        auto entity = entityManager.getEntity(currentGossip.npcGuid);
+        if (entity) {
+            glm::vec3 npcPos(entity->getX(), entity->getY(), entity->getZ());
+            npcGreetingCallback_(currentGossip.npcGuid, npcPos);
+        }
+    }
 }
 
 void GameHandler::handleGossipComplete(network::Packet& packet) {

src/rendering/renderer.cpp

@@ -37,6 +37,7 @@
 #include "audio/footstep_manager.hpp"
 #include "audio/activity_sound_manager.hpp"
 #include "audio/mount_sound_manager.hpp"
+#include "audio/npc_voice_manager.hpp"
 #include <GL/glew.h>
 #include <glm/gtc/matrix_transform.hpp>
 #include <glm/gtx/euler_angles.hpp>
@@ -342,6 +343,7 @@ bool Renderer::initialize(core::Window* win) {
     footstepManager = std::make_unique<audio::FootstepManager>();
     activitySoundManager = std::make_unique<audio::ActivitySoundManager>();
     mountSoundManager = std::make_unique<audio::MountSoundManager>();
+    npcVoiceManager = std::make_unique<audio::NpcVoiceManager>();
 
     // Underwater full-screen tint overlay (applies to all world geometry).
     underwaterOverlayShader = std::make_unique<Shader>();
@@ -2132,6 +2134,12 @@ bool Renderer::loadTerrainArea(const std::string& mapName, int centerX, int cent
             activitySoundManager->initialize(cachedAssetManager);
         }
     }
+    if (mountSoundManager && cachedAssetManager) {
+        mountSoundManager->initialize(cachedAssetManager);
+    }
+    if (npcVoiceManager && cachedAssetManager) {
+        npcVoiceManager->initialize(cachedAssetManager);
+    }
 
     // Wire WMO, M2, and water renderer to camera controller
     if (cameraController && wmoRenderer) {