Add goblin voice support for NPCs

- Added GOBLIN_MALE and GOBLIN_FEMALE to VoiceType enum
- Load greeting, farewell, vendor, and pissed sounds for goblin NPCs
- Prevents goblins from falling back to generic voice flag
- Uses proper goblin sound files from Goblin character folder

include/audio/npc_voice_manager.hpp

@@ -36,6 +36,8 @@ enum class VoiceType {
     UNDEAD_FEMALE,
     GNOME_MALE,
     GNOME_FEMALE,
+    GOBLIN_MALE,
+    GOBLIN_FEMALE,
     GENERIC,  // Fallback
 };