[refactor] Break Application::getInstance() from GameHandler

Introduce `GameServices` struct — an explicit dependency bundle that
`Application` populates and passes to `GameHandler` at construction time.
Eliminates all 47 hidden `Application::getInstance()` calls in
`src/game/*.cpp`, completing SOLID-D (dependency-inversion) cleanup.

Changes:
- New `include/game/game_services.hpp` — `struct GameServices` carrying
  pointers to `Renderer`, `AssetManager`, `ExpansionRegistry`, and two
  taxi-mount display IDs
- `GameHandler(GameServices&)` replaces default constructor; exposes
  `services() const` accessor for domain handlers
- `Application` holds `game::GameServices gameServices_`; populates it
  after all subsystems are created, then constructs `GameHandler`
  (fixes latent init-order bug: `GameHandler` was previously created
  before `AssetManager` / `ExpansionRegistry`)
- `game_handler.cpp`: duplicate `isActiveExpansion` / `isClassicLikeExpansion` /
  `isPreWotlk` anonymous-namespace helpers removed; `game_utils.hpp`
  included instead
- All domain handlers (`InventoryHandler`, `SpellHandler`, `MovementHandler`,
  `CombatHandler`, `QuestHandler`, `SocialHandler`, `WardenHandler`) replace
  `Application::getInstance().getXxx()` with `owner_.services().xxx`

include/core/application.hpp

@@ -3,6 +3,7 @@
 #include "core/window.hpp"
 #include "core/input.hpp"
 #include "game/character.hpp"
+#include "game/game_services.hpp"
 #include "pipeline/blp_loader.hpp"
 #include <memory>
 #include <string>
@@ -126,6 +127,7 @@ private:
 
     static Application* instance;
 
+    game::GameServices gameServices_;
     std::unique_ptr<Window> window;
     std::unique_ptr<rendering::Renderer> renderer;
     std::unique_ptr<ui::UIManager> uiManager;