Add plasmoid scaffold: metadata.json + config schema

Plasma/Applet package metadata (tray applet, id sk.houmeres.synologynas)
and the KConfigXT schema (hosts JSON, mount root, SMB version, options).
Passwords are never stored in config — they live in KWallet.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

package/contents/config/config.qml

@@ -0,0 +1,15 @@
+import QtQuick
+import org.kde.plasma.configuration
+
+ConfigModel {
+    ConfigCategory {
+        name: i18n("NAS Hosts")
+        icon: "network-server"
+        source: "config/ConfigHosts.qml"
+    }
+    ConfigCategory {
+        name: i18n("General")
+        icon: "configure"
+        source: "config/ConfigGeneral.qml"
+    }
+}