fix(waybar): show the power-profile indicator in the summer themes

custom/powerprofile only appeared in the generated bar -- its exec was a
writeShellScript store path, which can't go in the summer themes' static
whole-swap waybar.jsonc, so summer-day/night were missing it (the DND bell
already had parity). Promote powerProfileStatus/Cycle to named
writeShellScriptBins on PATH (waybar.nix home.packages) and reference them
by bare name, then add custom/powerprofile to both summer waybar.jsonc +
their waybar.css. Same pattern as the swaync bell.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

themes/summer-night/waybar.css

@@ -54,6 +54,7 @@ window#waybar {
 #workspaces,
 #pulseaudio,
 #network,
+#custom-powerprofile,
 #idle_inhibitor,
 #battery,
 #custom-notification,