Add internationalization support with English and French translations

- Introduced a new i18n module for managing translations using JSON files.
- Added English (en.json) and French (fr.json) translation files for UI elements.
- Implemented lazy initialization of the translator to load translations on demand.
- Added unit tests for translation lookup, fallback behavior, and available languages detection.

src/webdrop_bridge/main.py

@@ -15,6 +15,8 @@ from PySide6.QtWidgets import QApplication
 
 from webdrop_bridge.config import Config, ConfigurationError
 from webdrop_bridge.ui.main_window import MainWindow
+from webdrop_bridge.utils.i18n import get_translations_dir
+from webdrop_bridge.utils.i18n import initialize as i18n_init
 from webdrop_bridge.utils.logging import get_logger, setup_logging
 
 
@@ -50,6 +52,11 @@ def main() -> int:
         logger.info(f"Starting {config.app_name} v{config.app_version}")
         logger.debug(f"Configuration: {config}")
 
+        # Initialize internationalization
+        translations_dir = get_translations_dir()
+        i18n_init(config.language, translations_dir)
+        logger.debug(f"i18n initialized: language={config.language}, dir={translations_dir}")
+
     except ConfigurationError as e:
         print(f"Configuration error: {e}", file=sys.stderr)
         return 1