Fix dark-mode white flash when navigating between dashboard and library (#36785)

* Fix dark-mode white flash when navigating between dashboard and library

* Use userSettings object in layout-base.pug

* Move initial theme styles in a new file

* Sanitize data-initial-theme with a generic getInitialTheme helper

* Add getInitialTheme stub

GitOrigin-RevId: 80812093bbf75dc2a6f6f24710324a31a1930265

services/web/app/src/Features/Project/ProjectController.mjs

@@ -1079,7 +1079,7 @@ const _ProjectController = {
         user
       )
 
-      const initialLoadingScreenTheme = getInitialLoadingScreenTheme(
+      const initialLoadingScreenTheme = UserSettingsHelper.getInitialTheme(
         userSettings?.overallTheme
       )
 
@@ -1469,19 +1469,6 @@ const _ProjectController = {
   },
 }
 
-function getInitialLoadingScreenTheme(overallThemeSetting) {
-  switch (overallThemeSetting) {
-    case 'light-':
-      return 'light'
-    case '':
-      return 'dark'
-    case 'system':
-      return 'system'
-    default:
-      return 'dark'
-  }
-}
-
 const defaultSettingsForAnonymousUser = userId => ({
   id: userId,
   ace: {

services/web/app/src/Features/Project/ProjectListController.mjs

@@ -664,6 +664,7 @@ async function projectListPage(req, res, next) {
     userAffiliations,
     userEmails,
     userSettings,
+    initialTheme: UserSettingsHelper.getInitialTheme(userSettings.overallTheme),
     reconfirmedViaSAML,
     allInReconfirmNotificationPeriods,
     survey,

services/web/app/src/Features/Project/UserSettingsHelper.mjs

@@ -33,6 +33,19 @@ function buildRefProviderSettings(settings) {
   }
 }
 
+function getInitialTheme(overallThemeSetting) {
+  switch (overallThemeSetting) {
+    case 'light-':
+      return 'light'
+    case '':
+      return 'dark'
+    case 'system':
+      return 'system'
+    default:
+      return 'dark'
+  }
+}
+
 async function buildUserSettings(_req, _res, user) {
   return {
     mode: user.ace.mode,
@@ -63,4 +76,5 @@ async function buildUserSettings(_req, _res, user) {
 
 export default {
   buildUserSettings,
+  getInitialTheme,
 }