Fix review comments on Moonbase theme

- Fix CSS selector: use :not(.player-delete) instead of :not([class=".player-delete"])
- Fix MuiFormHelperText override structure: target error key directly
- Remove empty icon: {} and avatar: {} from NDLogin overrides
- Use comma-separated rgba syntax and hex for linear-gradient

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/themes/moonbase.css.js

@@ -48,7 +48,7 @@ const stylesheet = `
 .audio-lists-panel-content .audio-item.playing, .audio-lists-panel-content .audio-item.playing svg {
     color: #d4a039
 }
-.audio-lists-panel-content .audio-item:active .group:not([class=".player-delete"]) svg, .audio-lists-panel-content .audio-item:hover .group:not([class=".player-delete"]) svg {
+.audio-lists-panel-content .audio-item:active .group:not(.player-delete) svg, .audio-lists-panel-content .audio-item:hover .group:not(.player-delete) svg {
     color: #d4a039
 }
 

ui/src/themes/moonbase.js

@@ -41,14 +41,10 @@ export default {
       },
     },
     MuiFormHelperText: {
-      root: {
-        Mui: {
       error: {
         color: '#c45c3c',
       },
     },
-      },
-    },
     MuiTableHead: {
       root: {
         color: '#8a8278',
@@ -69,7 +65,6 @@ export default {
       systemNameLink: {
         color: '#d4a039',
       },
-      icon: {},
       welcome: {
         color: '#e5ddd3',
       },
@@ -77,7 +72,6 @@ export default {
         minWidth: 300,
         background: '#1e1e1c',
       },
-      avatar: {},
       button: {
         boxShadow: '3px 3px 5px #0a0a09',
       },
@@ -85,7 +79,7 @@ export default {
     NDMobileArtistDetails: {
       bgContainer: {
         background:
-          'linear-gradient(to bottom, rgba(10 10 9 / 72%), rgb(20 20 19))!important',
+          'linear-gradient(to bottom, rgba(10, 10, 9, 0.72), #141413)!important',
       },
     },
   },