Add ToastManager class for displaying notifications in the editor

- Implemented ToastManager to manage and display toast notifications with different types (info, success, warning, error).
- Introduced a Toast struct to encapsulate message details and time-to-live (TTL) for each notification.
- Integrated ImGui for rendering notifications on the screen, allowing for dynamic updates and automatic removal based on TTL.

src/app/editor/system/toast_manager.h

@@ -0,0 +1,76 @@
+#ifndef YAZE_APP_EDITOR_SYSTEM_TOAST_MANAGER_H
+#define YAZE_APP_EDITOR_SYSTEM_TOAST_MANAGER_H
+
+#include <deque>
+#include <string>
+
+#include "imgui/imgui.h"
+
+namespace yaze {
+namespace editor {
+
+enum class ToastType { kInfo, kSuccess, kWarning, kError };
+
+struct Toast {
+  std::string message;
+  ToastType type = ToastType::kInfo;
+  float ttl_seconds = 3.0f;
+};
+
+class ToastManager {
+ public:
+  void Show(const std::string &message, ToastType type = ToastType::kInfo,
+            float ttl_seconds = 3.0f) {
+    toasts_.push_back({message, type, ttl_seconds});
+  }
+
+  void Draw() {
+    if (toasts_.empty()) return;
+    ImGuiIO &io = ImGui::GetIO();
+    ImVec2 pos(io.DisplaySize.x - 10.f, 40.f);
+
+    // Iterate copy so we can mutate ttl while drawing ordered from newest.
+    for (auto it = toasts_.begin(); it != toasts_.end();) {
+      Toast &t = *it;
+      ImVec4 bg;
+      switch (t.type) {
+        case ToastType::kInfo: bg = ImVec4(0.10f, 0.10f, 0.10f, 0.85f); break;
+        case ToastType::kSuccess: bg = ImVec4(0.10f, 0.30f, 0.10f, 0.85f); break;
+        case ToastType::kWarning: bg = ImVec4(0.30f, 0.25f, 0.05f, 0.90f); break;
+        case ToastType::kError: bg = ImVec4(0.40f, 0.10f, 0.10f, 0.90f); break;
+      }
+      ImGui::SetNextWindowBgAlpha(bg.w);
+      ImGui::SetNextWindowPos(pos, ImGuiCond_Always, ImVec2(1.f, 0.f));
+      ImGuiWindowFlags flags = ImGuiWindowFlags_NoDecoration |
+                               ImGuiWindowFlags_AlwaysAutoResize |
+                               ImGuiWindowFlags_NoSavedSettings |
+                               ImGuiWindowFlags_NoNav;
+      ImGui::PushStyleColor(ImGuiCol_WindowBg, bg);
+      if (ImGui::Begin("##toast", nullptr, flags)) {
+        ImGui::TextUnformatted(t.message.c_str());
+      }
+      ImGui::End();
+      ImGui::PopStyleColor(1);
+
+      // Decrease TTL
+      t.ttl_seconds -= io.DeltaTime;
+      if (t.ttl_seconds <= 0.f) {
+        it = toasts_.erase(it);
+      } else {
+        // Next toast stacks below
+        pos.y += ImGui::GetItemRectSize().y + 6.f;
+        ++it;
+      }
+    }
+  }
+
+ private:
+  std::deque<Toast> toasts_;
+};
+
+}  // namespace editor
+}  // namespace yaze
+
+#endif  // YAZE_APP_EDITOR_SYSTEM_TOAST_MANAGER_H
+
+