core (constants): Fix path for hidden config files in $HOME:

Config file can be hidden in $HOME (`~/.libervia.toml`), and the path was wrongly handled
probably following a change to use `Path`.

libervia/backend/core/constants.py

@@ -60,7 +60,6 @@ class Const:
         Path("/etc/_"),
         Path("/etc/"),
         Path.home(),
-        Path.home() / ".",
         xdg_config_home / APP_NAME,
         # We use backend root as last config path, this is useful for per instance
         # configurations.
@@ -81,6 +80,9 @@ class Const:
     for p in CONFIG_PATHS:
         CONFIG_FILES.append(p / f"{APP_NAME_FILE}.toml")
 
+    # In $HOME, the config file can be hidden.
+    CONFIG_FILES.append(Path.home() / f".{APP_NAME_FILE}.toml")
+
     RUNTIME_DIR = xdg_runtime_dir / APP_NAME_FILE
 
     ## Runtime ##