Refactor/code cleanup (#37)

* fix imports
remove unused imports
use full import path
sort import (1. Standard Library, 2. Third-Party, 3. Local) in alphabetic.

* - remove: Method 3 from src.core.ytsage_downlader:cleanup_subtitle_file
  - it could delete the subtitle file of other movies if it present in same directory as it scane recursively.

- refactor: migrate from os.path to pathlib.Path for path handling
  - Replaced os.path methods with pathlib.Path to improve readability,
  - avoid repeatation.
  - cross-platform compatibility, and maintain cleaner code.

- improve: enhance code readability
  - Standardized string literals to use double quotes for consistency
  - Removed unnecessary spaces to maintain cleaner formatting
  - Applied code formatting for better readability and maintainability

* - add: ytsage_constants.py file for one place to store all constants.

- imporve: return type hint for function.

- remove: src/gui/ytsage_gui_dialogs.py file to avoid repetation
  - src/gui/dialogs is renamed to src/gui/ytsage_gui_dialogs for same naming convection. (future import will remains same)
  - use of src/gui/ytsage_gui_dialogs/__init__.py to import the dilogs modules.

- change: variable self.parent to self._parent so it does not overwrite the parent()
  - add type hint checking.

* - refactor: QMetaObject.invokeMethod to Signal
  - I encounter error with incokeMethod. Could not solve it.
  - So, Changed it to Signal to match app code language.

- implement: the ytsage_constants.py to code
  - remove: unnecessary logic
  - remove: repetitive code logic.

- update: yt-dlp logic for src\gui\ytsage_gui_dialogs\ytsage_dialogs_update:_update_binary
  - yt-dlp update logic will use `yt-dlp -U`

* refactor: remove unused imports and streamline code formatting across multiple files

main.py

@@ -1,8 +1,14 @@
 import sys
+
 from PySide6.QtWidgets import QApplication, QMessageBox
-from src.gui.ytsage_gui_main import YTSageApp  # Import the main application class from ytsage_gui_main
-from src.core.ytsage_yt_dlp import check_ytdlp_binary, setup_ytdlp, get_ytdlp_executable_path  # Import the new yt-dlp setup functions
+
 from src.core.ytsage_logging import logger
+from src.core.ytsage_yt_dlp import (  # Import the new yt-dlp setup functions
+    check_ytdlp_binary,
+    setup_ytdlp,
+)
+from src.gui.ytsage_gui_main import YTSageApp  # Import the main application class from ytsage_gui_main
+
 
 def show_error_dialog(message):
     error_dialog = QMessageBox()
@@ -12,28 +18,29 @@ def show_error_dialog(message):
     error_dialog.setWindowTitle("Error")
     error_dialog.exec()
 
+
 def main():
     try:
         logger.info("Starting YTSage application")
         app = QApplication(sys.argv)
-        
+
         # Get the expected binary path and check if it exists
-        expected_path = get_ytdlp_executable_path()
         if not check_ytdlp_binary():
             # No app-specific binary found, show setup dialog regardless of Python package
             logger.warning("No yt-dlp binary found, starting setup process")
             yt_dlp_path = setup_ytdlp()
             if yt_dlp_path == "yt-dlp":  # If user canceled or something went wrong
                 logger.warning("yt-dlp not configured properly")
-        
-        window = YTSageApp() # Instantiate the main application class
+
+        window = YTSageApp()  # Instantiate the main application class
         window.show()
         logger.info("Application window shown, entering main loop")
         sys.exit(app.exec())
     except Exception as e:
-        logger.critical(f"Critical application error: {str(e)}", exc_info=True)
-        show_error_dialog(f"Critical error: {str(e)}")
+        logger.critical(f"Critical application error: {e}", exc_info=True)
+        show_error_dialog(f"Critical error: {e}")
         sys.exit(1)
 
-if __name__ == '__main__':
-    main()
+
+if __name__ == "__main__":
+    main()