fix(themes): restore summer-night's blank notification bell icons

summer-night shipped with its custom/notification format-icons all empty
(the same Nerd Font glyph-loss seen in executive-slate/boreal), so its bar
showed a blank notification indicator regardless of state — while its
sibling summer-day kept the icons. Filled them in from summer-day so the
FontAwesome bell (U+F0F3) / bell-slash (U+F1F6) match across the pair.
Surgical edit — only the 8 icon values changed, hand-formatting untouched.

V1: builtins.fromJSON parses; icons now byte-identical to summer-day; zero
empty glyph fields remain across all four whole-swap bars.

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

themes/summer-night/waybar.jsonc

@@ -138,14 +138,14 @@
     "on-click": "swaync-client -t -sw",
     "on-click-right": "swaync-client -d -sw",
     "format-icons": {
-      "none": "",
-      "notification": "",
-      "dnd-none": "",
-      "dnd-notification": "",
-      "inhibited-none": "",
-      "inhibited-notification": "",
-      "dnd-inhibited-none": "",
-      "dnd-inhibited-notification": ""
+      "none": "",
+      "notification": "",
+      "dnd-none": "",
+      "dnd-notification": "",
+      "inhibited-none": "",
+      "inhibited-notification": "",
+      "dnd-inhibited-none": "",
+      "dnd-inhibited-notification": ""
     }
   },