main : Use pathlib instead of os.path

Removes every use of os.path and replaces it with the equivalent pathlib
method.
Allows to avoid importing os.

src/unisync/main.py

@@ -1,7 +1,6 @@
 # Copyright (C) 2025-2026 Paul Retourné
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-import os
 from pathlib import Path
 
 from unisync.argparser import create_argparser
@@ -14,15 +13,15 @@ def main():
     parser = create_argparser(unisync_sync, unisync_add, unisync_mount)
     cli_args = parser.parse_args()
 
-    config_path = os.path.expanduser("~/.config/unisync/config.ini")
+    config_path: Path = Path("~/.config/unisync/config.ini").expanduser()
     # Check if --config is set
-    if cli_args.config != None and os.path.isfile(cli_args.config):
+    if cli_args.config != None and Path(cli_args.config).is_file():
         config = load_config(cli_args.config)
-    elif os.path.isfile(config_path):
-        config = load_config(config_path)
+    elif config_path.is_file():
+        config = load_config(str(config_path))
     else:
         # TODO replace the next line with something to do if no config file is found
-        config = load_config(config_path)
+        config = load_config(str(config_path))
         pass
 
     # TODO make the command line arguments work and override the config options