feat: add keybinding manager for customizable action shortcuts

Implement KeybindingManager singleton class to support:
- Storing and loading keybinding configuration from ini files
- Querying whether an action's keybinding was pressed
- Runtime rebinding of actions to different keys
- Default keybinding set: C=Character, I=Inventory, S=Spellbook, K=Talents,
  L=Quests, M=Minimap, Esc=Settings, Enter=Chat

This is the foundation for user-customizable keybindings. Integration with
UI controls and replacement of hard-coded ImGui::IsKeyPressed calls will
follow in subsequent improvements.

include/ui/keybinding_manager.hpp

@@ -0,0 +1,82 @@
+#ifndef WOWEE_KEYBINDING_MANAGER_HPP
+#define WOWEE_KEYBINDING_MANAGER_HPP
+
+#include <imgui.h>
+#include <string>
+#include <unordered_map>
+#include <memory>
+
+namespace wowee::ui {
+
+/**
+ * Manages keybinding configuration for in-game actions.
+ * Supports loading/saving from config files and runtime rebinding.
+ */
+class KeybindingManager {
+public:
+    enum class Action {
+        TOGGLE_CHARACTER_SCREEN,
+        TOGGLE_INVENTORY,
+        TOGGLE_SPELLBOOK,
+        TOGGLE_TALENTS,
+        TOGGLE_QUESTS,
+        TOGGLE_MINIMAP,
+        TOGGLE_SETTINGS,
+        TOGGLE_CHAT,
+        ACTION_COUNT
+    };
+
+    static KeybindingManager& getInstance();
+
+    /**
+     * Check if an action's keybinding was just pressed.
+     * Uses ImGui::IsKeyPressed() internally with the bound key.
+     */
+    bool isActionPressed(Action action, bool repeat = false);
+
+    /**
+     * Get the currently bound key for an action.
+     */
+    ImGuiKey getKeyForAction(Action action) const;
+
+    /**
+     * Rebind an action to a different key.
+     */
+    void setKeyForAction(Action action, ImGuiKey key);
+
+    /**
+     * Reset all keybindings to defaults.
+     */
+    void resetToDefaults();
+
+    /**
+     * Load keybindings from config file.
+     */
+    void loadFromConfigFile(const std::string& filePath);
+
+    /**
+     * Save keybindings to config file.
+     */
+    void saveToConfigFile(const std::string& filePath) const;
+
+    /**
+     * Get human-readable name for an action.
+     */
+    static const char* getActionName(Action action);
+
+    /**
+     * Get all actions for iteration.
+     */
+    static constexpr int getActionCount() { return static_cast<int>(Action::ACTION_COUNT); }
+
+private:
+    KeybindingManager();
+
+    std::unordered_map<int, ImGuiKey> bindings_;  // action -> key
+
+    void initializeDefaults();
+};
+
+}  // namespace wowee::ui
+
+#endif  // WOWEE_KEYBINDING_MANAGER_HPP