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-night/waybar.css

@@ -53,7 +53,6 @@ window#waybar {
 #clock.date,
 #workspaces,
 #pulseaudio,
-#network,
 #custom-powerprofile,
 #idle_inhibitor,
 #battery,
@@ -75,6 +74,11 @@ window#waybar {
     color: @fg;
 }
 
+/* The power-profile speedometer glyph renders small in its em box. */
+#custom-powerprofile {
+  font-size: 17px;
+}
+
 #tray > .needs-attention {
     color: @green;
 }