feat(ui): point help new-content indicator at the updated tabs and elements

- Replace timestamp comparison (help_last_viewed vs a hardcoded date) with
  a content-version marker (data-help-content-version) read from the
  rendered modal markup, so badge state always reflects the content
  actually served
- Only mark content as viewed when the modal is opened while it contains
  new content; opening a stale pre-upgrade page no longer suppresses the
  badge after a refresh
- Flag the Replay Tutorial button itself with a 'New' chip (hidden by
  default, one-time glow animation) and scroll it into view when
  revealed; tab-level dots now mark getting-started and shortcuts
  instead of documentation
- Translate help.newContentBadge into all 9 locales, reusing the
  established help.documentation.newBadge renderings
- Add HelpManager content-version unit tests (12 cases)

locales/de.json

@@ -2028,7 +2028,8 @@
             "settings": "Einstellungen & Konfiguration",
             "extensions": "Erweiterungen",
             "newBadge": "NEU"
-        }
+        },
+        "newContentBadge": "NEU"
     },
     "update": {
         "title": "Nach Updates suchen",