fix: volume keys not working, add cursor theme, fix swayosd crash

[Hedayatbakhshi]

• Add capitain-cursor package to install list
• Set capitain-cursor as system cursor in env.conf, GTK settings.ini,
  and gsettings
• Fix XF86 audio key names (xf86 → XF86) in settings.json and
  keybindings template
• Add --config flag to swayosd-server startup to avoid crash from
  unsupported duration field
• Create local swayosd config.toml to override broken system config