[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/game/game_services.hpp

@@ -0,0 +1,23 @@
+#pragma once
+#include <cstdint>
+
+namespace wowee {
+namespace rendering { class Renderer; }
+namespace pipeline { class AssetManager; }
+namespace game { class ExpansionRegistry; }
+
+namespace game {
+
+// Explicit service dependencies for game handlers.
+// Owned by Application, passed by reference to GameHandler at construction.
+// Replaces hidden Application::getInstance() singleton access.
+struct GameServices {
+    rendering::Renderer* renderer = nullptr;
+    pipeline::AssetManager* assetManager = nullptr;
+    game::ExpansionRegistry* expansionRegistry = nullptr;
+    uint32_t gryphonDisplayId = 0;
+    uint32_t wyvernDisplayId = 0;
+};
+
+} // namespace game
+} // namespace wowee