feat(waybar): drop redundant network module, enlarge power-profile glyph

The network/wifi indicator duplicated nm-applet, which already sits in the
tray (services.network-manager-applet.enable), so remove it from the bar.
And the power-profile speedometer glyph rendered noticeably smaller than
the neighbouring indicators, so bump its font-size (+3pt generated; 20px
summer-day, 17px summer-night).

Applied to the generated bar (waybar.nix) and both whole-swap themes
(summer-day/night waybar.{jsonc,css}) for parity.

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

themes/summer-day/waybar.css

@@ -47,7 +47,6 @@ window#waybar {
 #clock-date,
 #workspaces,
 #pulseaudio,
-#network,
 #custom-powerprofile,
 #battery,
 #tray,
@@ -71,6 +70,11 @@ window#waybar {
   padding: 0px;
 }
 
+/* The power-profile speedometer glyph renders small in its em box. */
+#custom-powerprofile {
+  font-size: 20px;
+}
+
 #workspaces button.active {
   background-color: @blue;
   color: @bg0;