Add theme management and background rendering features

- Introduced a comprehensive theme management system, allowing users to load, save, and switch between multiple themes.
- Added support for various built-in themes, enhancing the visual customization of the application.
- Implemented a background renderer for improved visual effects in docking windows, including grid backgrounds and subtle animations.
- Enhanced the EditorManager UI with themed elements, providing a more cohesive and engaging user experience.
- Updated CMake configuration to include new theme and background renderer source files, ensuring proper integration into the build system.

src/app/gui/background_renderer.h

@@ -0,0 +1,96 @@
+#ifndef YAZE_APP_GUI_BACKGROUND_RENDERER_H
+#define YAZE_APP_GUI_BACKGROUND_RENDERER_H
+
+#include "imgui/imgui.h"
+#include "app/gui/color.h"
+
+namespace yaze {
+namespace gui {
+
+/**
+ * @class BackgroundRenderer
+ * @brief Renders themed background effects for docking windows
+ */
+class BackgroundRenderer {
+public:
+  struct GridSettings {
+    float grid_size = 32.0f;           // Size of grid cells
+    float line_thickness = 1.0f;      // Thickness of grid lines
+    float opacity = 0.12f;            // Subtle but visible opacity
+    float fade_distance = 400.0f;     // Distance over which grid fades
+    bool enable_animation = false;    // Animation toggle (default off)
+    bool enable_breathing = false;    // Color breathing effect toggle (default off)
+    bool radial_fade = true;          // Re-enable subtle radial fade
+    bool enable_dots = false;         // Use dots instead of lines
+    float dot_size = 2.0f;            // Size of grid dots
+    float animation_speed = 1.0f;     // Animation speed multiplier
+    float breathing_speed = 1.5f;     // Breathing effect speed
+    float breathing_intensity = 0.3f; // How much color changes during breathing
+  };
+  
+  static BackgroundRenderer& Get();
+  
+  // Main rendering functions
+  void RenderDockingBackground(ImDrawList* draw_list, const ImVec2& window_pos, 
+                              const ImVec2& window_size, const Color& theme_color);
+  void RenderGridBackground(ImDrawList* draw_list, const ImVec2& window_pos, 
+                           const ImVec2& window_size, const Color& grid_color);
+  void RenderRadialGradient(ImDrawList* draw_list, const ImVec2& center, 
+                           float radius, const Color& inner_color, const Color& outer_color);
+  
+  // Configuration
+  void SetGridSettings(const GridSettings& settings) { grid_settings_ = settings; }
+  const GridSettings& GetGridSettings() const { return grid_settings_; }
+  
+  // Animation
+  void UpdateAnimation(float delta_time);
+  void SetAnimationEnabled(bool enabled) { grid_settings_.enable_animation = enabled; }
+  
+  // Theme integration
+  void UpdateForTheme(const Color& primary_color, const Color& background_color);
+  
+  // UI for settings
+  void DrawSettingsUI();
+  
+private:
+  BackgroundRenderer() = default;
+  
+  GridSettings grid_settings_;
+  float animation_time_ = 0.0f;
+  Color cached_grid_color_{0.5f, 0.5f, 0.5f, 0.1f};
+  
+  // Helper functions
+  float CalculateRadialFade(const ImVec2& pos, const ImVec2& center, float max_distance) const;
+  ImU32 BlendColorWithFade(const Color& base_color, float fade_factor) const;
+  void DrawGridLine(ImDrawList* draw_list, const ImVec2& start, const ImVec2& end, 
+                   ImU32 color, float thickness) const;
+  void DrawGridDot(ImDrawList* draw_list, const ImVec2& pos, ImU32 color, float size) const;
+};
+
+/**
+ * @class DockSpaceRenderer
+ * @brief Enhanced docking space with themed background effects
+ */
+class DockSpaceRenderer {
+public:
+  static void BeginEnhancedDockSpace(ImGuiID dockspace_id, const ImVec2& size = ImVec2(0, 0), 
+                                    ImGuiDockNodeFlags flags = 0);
+  static void EndEnhancedDockSpace();
+  
+  // Configuration
+  static void SetBackgroundEnabled(bool enabled) { background_enabled_ = enabled; }
+  static void SetGridEnabled(bool enabled) { grid_enabled_ = enabled; }
+  static void SetEffectsEnabled(bool enabled) { effects_enabled_ = enabled; }
+  
+private:
+  static bool background_enabled_;
+  static bool grid_enabled_;
+  static bool effects_enabled_;
+  static ImVec2 last_dockspace_pos_;
+  static ImVec2 last_dockspace_size_;
+};
+
+} // namespace gui
+} // namespace yaze
+
+#endif // YAZE_APP_GUI_BACKGROUND_RENDERER_H