Add install.sh, uninstall.sh and README

Distro-agnostic installer (dep check, sudo helper+policy install, per-user
kpackagetool6 install/upgrade) and matching uninstaller; full public README
covering requirements, usage, architecture and security notes.

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

uninstall.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+#
+# uninstall.sh — remove the Synology NAS plasmoid, helper and polkit policy.
+# Mounted shares and stored KWallet passwords are left untouched.
+#
+set -eu
+
+APPLET_ID="sk.houmeres.synologynas"
+HELPER_DEST="/usr/lib/synology-nas/helper"
+POLICY_DEST="/usr/share/polkit-1/actions/sk.houmeres.synologynas.policy"
+
+say() { printf '==> %s\n' "$1"; }
+
+if kpackagetool6 --type Plasma/Applet --list 2>/dev/null | grep -qx "$APPLET_ID"; then
+    say "Removing plasmoid $APPLET_ID"
+    kpackagetool6 --type Plasma/Applet --remove "$APPLET_ID" || true
+fi
+
+say "Removing helper + polkit policy"
+sudo rm -f "$HELPER_DEST" "$POLICY_DEST"
+sudo rmdir /usr/lib/synology-nas 2>/dev/null || true
+
+cat <<EOF
+
+Done. Note: any currently mounted shares stay mounted (unmount them from the
+widget before uninstalling, or with 'umount'), and saved passwords remain in
+KWallet under the "Synology NAS" folder — remove them with kwalletmanager if
+you want them gone.
+EOF