Add mouse battery widget, Bolt Launcher rule, cursor size; fix theme symlink

- waybar: add custom/mouse-battery module and mouse-battery.sh script
- niri: add Bolt Launcher floating rule; switch RuneLite to floating
- environment.d: set XCURSOR_SIZE=36
- install.sh: add symlinks for theme/colors.css and mouse-battery.sh (fixes @import path)
- .gitignore: exclude nohup.out

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

waybar/mouse-battery.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+# Generic mouse battery script for Waybar
+
+MOUSE_BATTERY=$(upower -e | grep -i mouse | head -n1)
+
+if [ -n "$MOUSE_BATTERY" ]; then
+	upower -i "$MOUSE_BATTERY" | awk '/percentage:/ { print $2 }'
+else
+	echo "N/A"
+fi