chore(config): 🎨 restructure lazygit theme configuration

Move theme settings under `gui` section to match latest lazygit
configuration format. This aligns with the updated configuration
structure introduced in recent versions.

The color values remain unchanged - only the nesting structure has been
modified to maintain compatibility with lazygit's configuration schema
requirements.

home/.config/lazygit/config.yml

@@ -1,4 +1,5 @@
-theme:
+gui:
+  theme:
     activeBorderColor:
       - '#8bd5ca'
       - bold
@@ -19,5 +20,5 @@ theme:
     searchingActiveBorderColor:
       - '#eed49f'
 
-authorColors:
+  authorColors:
     '*': '#b7bdf8'