Add localization for post-processing status messages

Introduces new translation keys for post-processing status messages ('merging formats' and 'removing sponsor segments') in all supported languages. Updates code to use these i18n keys in both downloader and GUI, improving localization and consistency of user-facing messages.

src/core/ytsage_downloader.py

@@ -666,10 +666,10 @@ class DownloadThread(QThread):
 
         # Check for post-processing
         if "[Merger]" in line or "Merging formats" in line:
-            self.status_signal.emit("✨ Post-processing: Merging formats...")
+            self.status_signal.emit(_("download.merging_formats"))
             self.progress_signal.emit(95)
         elif "SponsorBlock" in line:
-            self.status_signal.emit("✨ Post-processing: Removing sponsor segments...")
+            self.status_signal.emit(_("download.removing_sponsor_segments"))
             self.progress_signal.emit(97)
         elif "Deleting original file" in line:
             self.progress_signal.emit(98)

src/gui/ytsage_gui_main.py

@@ -1891,7 +1891,7 @@ class YTSageApp(QMainWindow, FormatTableMixin, VideoInfoMixin):  # Inherit from
             self.audio_button.setChecked(False)
             self.filter_formats()
 
-            self.signals.update_status.emit("Analysis complete!")
+            self.signals.update_status.emit(_("main_ui.analysis_complete"))
 
         except subprocess.TimeoutExpired:
             logger.error("Analysis timed out. Please try again.")