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/asus/fix-mic.sh

@@ -0,0 +1,15 @@
+# Fix internal mic gain on ASUS ROG laptops with Realtek ALC285.
+# The mic boost is way too high by default, causing clipping.
+# Sets levels and stores ALSA state so it persists across reboots.
+
+if omarchy-hw-asus-rog; then
+  for card in /proc/asound/card*/codec*; do
+    if grep -q "ALC285" "$card" 2>/dev/null; then
+      cardnum=$(echo "$card" | grep -oP 'card\K\d+')
+      amixer -c "$cardnum" set 'Internal Mic Boost' 0 >/dev/null 2>&1 || true
+      amixer -c "$cardnum" set 'Capture' 70% unmute >/dev/null 2>&1 || true
+      sudo alsactl store "$cardnum" 2>/dev/null || true
+      break
+    fi
+  done
+fi