Make setup ISO-only

Remove legacy online installer entrypoints, collapse migrations for 4.0, and move setup responsibilities into target-side system, hardware, and user commands.

install/user/hardware/bluetooth.sh

@@ -0,0 +1,13 @@
+mkdir -p ~/.config/wireplumber/wireplumber.conf.d/
+cp "$OMARCHY_PATH/default/wireplumber/wireplumber.conf.d/bluetooth-a2dp-autoconnect.conf" ~/.config/wireplumber/wireplumber.conf.d/
+
+# Quickshell.Bluetooth has no Agent API, so the omarchy.bluetooth plugin
+# can't answer the auth prompts bluez issues during pair(). bt-agent registers
+# a NoInputNoOutput agent on the system bus so pair() actually completes.
+mkdir -p ~/.config/systemd/user/
+cp "$OMARCHY_PATH/config/systemd/user/bt-agent.service" ~/.config/systemd/user/
+if declare -F omarchy_user_systemctl_enable >/dev/null; then
+  omarchy_user_systemctl_enable bt-agent.service
+else
+  systemctl --user enable bt-agent.service
+fi