logger: add a dedicated QML logging Singleton

- adds log.info/error/debug/warn/fatal
- adds ability to write logs to any file
- add CLI options in addition to env to set log levels

quickshell/Services/VPNService.qml

@@ -4,9 +4,11 @@ pragma ComponentBehavior: Bound
 import QtQuick
 import Quickshell
 import qs.Common
+import qs.Services
 
 Singleton {
     id: root
+    readonly property var log: Log.scoped("VPNService")
 
     readonly property bool available: DMSNetworkService.vpnAvailable
 
@@ -48,7 +50,7 @@ Singleton {
         DMSService.sendRequest("network.vpn.plugins", null, response => {
             pluginsLoading = false;
             if (response.error) {
-                console.warn("VPNService: Failed to fetch plugins:", response.error);
+                log.warn("Failed to fetch plugins:", response.error);
                 return;
             }
             if (!response.result)