core (constants): Use runtime dir:

PID and PB bridge socket were using temporary directory, but the good practice is to use
XDG_RUNTIME_DIR instead.

libervia/backend/core/constants.py

@@ -38,6 +38,7 @@ xdg_config_dirs = [
     d for d in os.environ.get("XDG_CONFIG_DIRS", "/etc/xdg").split(":") if d
 ]
 xdg_data_home = Path(os.environ.get("XDG_DATA_HOME") or Path.home() / ".local/share")
+xdg_runtime_dir = Path(os.environ.get("XDG_RUNTIME_DIR") or f"/run/user/{os.getuid()}")
 
 
 class Const:
@@ -80,7 +81,7 @@ class Const:
     for p in CONFIG_PATHS:
         CONFIG_FILES.append(p / f"{APP_NAME_FILE}.toml")
 
-    TEMP_DIR = Path(tempfile.gettempdir(), f"{APP_NAME_FILE}_{logged_user}")
+    RUNTIME_DIR = xdg_runtime_dir / APP_NAME_FILE
 
     ## Runtime ##
     PLUGIN_EXT = "py"

libervia/backend/tools/config.py

@@ -167,10 +167,10 @@ class PbBridgeSettings(ConfigOptions):
         default=8789, description='TCP port to use when ``connection_type`` is "socket"'
     )
     socket_dir: DirectoryPathAuto = Field(
-        default=C.TEMP_DIR,
+        default=C.RUNTIME_DIR,
         description=(
             "Directory where the UNIX socket file will be created when using unix_socket"
-            " connection type."
+            " connection type. Default is the user's runtime directory."
         ),
     )
     host: str = Field(
@@ -263,10 +263,10 @@ class CommonSettings(ConfigOptions):
     )
     log_fmt: str | None = Field(default=None, description="Log message format")
     pid_dir: DirectoryPathAuto = Field(
-        default=C.TEMP_DIR,
+        default=C.RUNTIME_DIR,
         description=(
-            "Directory where PID files will be stored. Default is a subdirectory of the"
-            " system's temporary directory."
+            "Directory where PID files will be stored. Default is the user's runtime"
+            " directory."
         ),
     )
     xmpp_domain: str = Field(