feat: add Lua 5.1 addon system with .toc loader and /run command

Foundation for WoW-compatible addon support:

- Vendor Lua 5.1.5 source as a static library (extern/lua-5.1.5)
- TocParser: parses .toc files (## directives + file lists)
- LuaEngine: Lua 5.1 VM with sandboxed stdlib (no io/os/debug),
  WoW-compatible print() that outputs to chat, GetTime() stub
- AddonManager: scans Data/interface/AddOns/ for .toc files,
  loads .lua files on world entry, skips LoadOnDemand addons
- /run <code> slash command for inline Lua execution
- HelloWorld test addon that prints to chat on load

Integration: AddonManager initialized after asset manager, addons
loaded once on first world entry, reset on logout. XML frame
parsing is deferred to a future step.

include/core/application.hpp

@@ -26,6 +26,7 @@ namespace auth { class AuthHandler; }
 namespace game { class GameHandler; class World; class ExpansionRegistry; }
 namespace pipeline { class AssetManager; class DBCLayout; struct M2Model; struct WMOModel; }
 namespace audio { enum class VoiceType; }
+namespace addons { class AddonManager; }
 
 namespace core {
 
@@ -62,6 +63,7 @@ public:
     game::GameHandler* getGameHandler() { return gameHandler.get(); }
     game::World* getWorld() { return world.get(); }
     pipeline::AssetManager* getAssetManager() { return assetManager.get(); }
+    addons::AddonManager* getAddonManager() { return addonManager_.get(); }
     game::ExpansionRegistry* getExpansionRegistry() { return expansionRegistry_.get(); }
     pipeline::DBCLayout* getDBCLayout() { return dbcLayout_.get(); }
     void reloadExpansionData(); // Reload DBC layouts, opcodes, etc. after expansion change
@@ -129,6 +131,8 @@ private:
     std::unique_ptr<game::GameHandler> gameHandler;
     std::unique_ptr<game::World> world;
     std::unique_ptr<pipeline::AssetManager> assetManager;
+    std::unique_ptr<addons::AddonManager> addonManager_;
+    bool addonsLoaded_ = false;
     std::unique_ptr<game::ExpansionRegistry> expansionRegistry_;
     std::unique_ptr<pipeline::DBCLayout> dbcLayout_;