feat: implement logging service with file output

- setup_logging() creates logs/ dir and writes timestamped log file
- format: asctime name levelname message
- falls back to console-only if log dir is not writable
- main.py now calls setup_logging() at startup and logs app name/version

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main.py

@@ -1,18 +1,26 @@
+import logging
 import sys
 
 from PySide6.QtWidgets import QApplication
 
 from app.main_window import MainWindow
-from version import APP_NAME
+from services.log_service import setup_logging
+from version import APP_NAME, APP_VERSION
+
+logger = logging.getLogger(__name__)
 
 
 def main():
+    setup_logging()
+    logger.info("Application starting: %s %s", APP_NAME, APP_VERSION)
+
     app = QApplication(sys.argv)
     app.setApplicationName(APP_NAME)
 
     window = MainWindow()
     window.show()
 
+    logger.info("Main window displayed")
     return app.exec()