New: Auto theme option to match OS theme

Co-authored-by: Qstick <qstick@gmail.com>

frontend/src/Styles/Themes/index.js

@@ -1,7 +1,11 @@
 import * as dark from './dark';
 import * as light from './light';
 
+const defaultDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
+const auto = defaultDark ? { ...dark } : { ...light };
+
 export default {
+  auto,
   light,
   dark
 };

src/NzbDrone.Core/Configuration/ConfigFileProvider.cs

@@ -206,7 +206,7 @@ namespace NzbDrone.Core.Configuration
         public string PostgresMainDb => _postgresOptions?.MainDb ?? GetValue("PostgresMainDb", "prowlarr-main", persist: false);
         public string PostgresLogDb => _postgresOptions?.LogDb ?? GetValue("PostgresLogDb", "prowlarr-log", persist: false);
         public int PostgresPort => (_postgresOptions?.Port ?? 0) != 0 ? _postgresOptions.Port : GetValueInt("PostgresPort", 5432, persist: false);
-        public string Theme => GetValue("Theme", "light", persist: false);
+        public string Theme => GetValue("Theme", "auto", persist: false);
         public bool LogSql => GetValueBoolean("LogSql", false, persist: false);
         public int LogRotate => GetValueInt("LogRotate", 50, persist: false);
         public bool FilterSentryEvents => GetValueBoolean("FilterSentryEvents", true, persist: false);

src/NzbDrone.Core/Localization/Core/en.json

@@ -404,7 +404,7 @@
   "TestAllApps": "Test All Apps",
   "TestAllClients": "Test All Clients",
   "TestAllIndexers": "Test All Indexers",
-  "ThemeHelpText": "Change Prowlarr UI theme, inspired by {0}",
+  "ThemeHelpText": "Change Application UI Theme, 'Auto' Theme will use your OS Theme to set Light or Dark mode. Inspired by {0}",
   "Time": "Time",
   "Title": "Title",
   "Today": "Today",