Rename every remaining voxip name to daynivo, with a one-time migration

Services (daynivo-kiosk-*, daynivo-network-guard, daynivo-boot-import),
programs in /usr/lib/daynivo-kiosk, folders /etc, /var/lib, /var/log and
/var/cache daynivo-kiosk*, the system user daynivo, DAYNIVO_* settings,
the plymouth theme, network profiles daynivo-eth0/wlan0, the image stage
and its first user daynivoadmin.

install.sh moves a kiosk installed up to 1.2.x over once: old services
stopped and removed, folders moved (configuration, password, browser
profile, logs) with symlinks under the old names, the voxip user renamed
with the same uid, network profiles renamed unless a change awaits
confirmation, and old leftovers removed. Tested by upgrading a configured
1.2.0 installation in a container, and running the install a second time.

Old names keep working where people type or place them: voxip-config.json,
voxip-authorized_keys, voxip-network-reset, voxip-kiosk-ctl, and
VOXIP_DEFAULT_URL / VOXIP_DEVICE_NAME for image builds.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

config/plymouth/daynivo-kiosk/daynivo-kiosk.script

@@ -0,0 +1,12 @@
+# Daynivo Kiosk boot splash: logo.png centred on white, at most half the screen.
+# Replace logo.png (any size, PNG with transparency) for a different logo.
+Window.SetBackgroundTopColor(1, 1, 1);
+Window.SetBackgroundBottomColor(1, 1, 1);
+
+logo = Image("logo.png");
+scale = Math.Min(Window.GetWidth() * 0.5 / logo.GetWidth(), Window.GetHeight() * 0.5 / logo.GetHeight());
+if (scale > 1) scale = 1;
+logo = logo.Scale(logo.GetWidth() * scale, logo.GetHeight() * scale);
+
+sprite = Sprite(logo);
+sprite.SetPosition((Window.GetWidth() - logo.GetWidth()) / 2, (Window.GetHeight() - logo.GetHeight()) / 2, 0);