docs: restructure i18n docs into top-level Flow section

articles/building-apps/forms-data/create-custom-field/index.adoc

@@ -652,7 +652,7 @@ Always call `updateI18n()` whenever texts should be refreshed, for example, insi
 
 === Further Reading
 
-For more details on localization in Vaadin, see the <<{articles}/flow/advanced/i18n-localization#,Localization>> article.
+For more details on localization in Vaadin, see the <<{articles}/flow/i18n#,Localization>> article.
 
 == Accessibility
 

articles/components/date-picker/date-formats.adoc

@@ -17,7 +17,7 @@ Two-digit year formats are supported, and you can set the <<two-digit-year-forma
 ifdef::flow[]
 == Using Java Locales in Flow
 
-By default, Date Picker displays and parses dates using the user's locale (<<{articles}/flow/advanced/i18n-localization#locale-selection-for-new-session,reference>>). Setting a specific locale ensures that all users see the same format.
+By default, Date Picker displays and parses dates using the user's locale (<<{articles}/flow/i18n#locale-selection,reference>>). Setting a specific locale ensures that all users see the same format.
 
 In the example here, the Date Picker is set to the date format used in Finland:
 

articles/flow/configuration/properties.adoc

@@ -228,7 +228,7 @@ Default: 300 seconds (i.e., 5 minutes) +
 Mode: Runtime
 
 `**i18n.provider**`::
-Sets the fully-qualified name for the internationalization provider class. To translate strings for localization, the application should implement the `I18NProvider` interface and define the class name in the `i18n.provider` property. See the <<{articles}/flow/advanced/i18n-localization#, Localization documentation>> for details. +
+Sets the fully-qualified name for the internationalization provider class. To translate strings for localization, the application should implement the `I18NProvider` interface and define the class name in the `i18n.provider` property. See the <<{articles}/flow/i18n#, Localization documentation>> for details. +
 Default: `null` +
 Mode: Runtime