feat: [FC-0044] Unit page header section (#808)

* feat: create Unit page and add page header functionality

* fix: after code review

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Co-authored-by: monteri <lansevermore>

.env.development

@@ -34,7 +34,6 @@ ENABLE_PROGRESS_GRAPH_SETTINGS=false
 ENABLE_TEAM_TYPE_SETTING=false
 ENABLE_NEW_EDITOR_PAGES=true
 ENABLE_NEW_VIDEO_UPLOAD_PAGE = false
-ENABLE_UNIT_PAGE = false
 ENABLE_VIDEO_UPLOAD_PAGE_LINK_IN_CONTENT_DROPDOWN = false
 ENABLE_TAGGING_TAXONOMY_PAGES = true
 BBB_LEARN_MORE_URL=''
@@ -43,3 +42,4 @@ HOTJAR_VERSION=6
 HOTJAR_DEBUG=true
 INVITE_STUDENTS_EMAIL_TO="someone@domain.com"
 AI_TRANSLATIONS_BASE_URL='http://localhost:18760'
+PREVIEW_BASE_URL='http://preview.localhost:18000'