Fix the label corruption issue

src/printers/FakePrinter.hpp

@@ -86,6 +86,20 @@ class FakePrinter : public ::ptprnt::IPrinterDriver {
      */
     graphics::Bitmap<graphics::ALPHA8> simulatePrinting(const graphics::MonochromeData& data);
 
+    /**
+     * @brief Save bitmap to PNG file using Cairo
+     * @param bitmap The bitmap to save
+     * @param filename Output filename
+     * @return true if successful
+     */
+    bool saveBitmapToPng(const graphics::Bitmap<graphics::ALPHA8>& bitmap, const std::string& filename) const;
+
+    /**
+     * @brief Generate timestamped filename for fake label output
+     * @return Filename like "fakelabel_20231011_123456.png"
+     */
+    std::string generateTimestampedFilename() const;
+
     std::unique_ptr<graphics::Bitmap<graphics::ALPHA8>> mLastPrint;
     bool mHasAttachedDevice = false;
     PrinterStatus mStatus{.tapeWidthMm = 12};  // Default to 12mm tape