feat(vocab): add dashboard learning summary and related endpoints

- Introduced `getDashboardLearningSummary` method in `VocabService` to provide a compact overview of enrolled courses and current lessons for users.
- Updated `vocabController` to include a new route for the dashboard widget, allowing users to access their learning summary.
- Enhanced `vocabRouter` to route requests for the new dashboard widget endpoint.
- Added localization support for the new dashboard features across multiple languages, improving user engagement and accessibility.
- Updated UI components to integrate the new dashboard widget, ensuring a seamless user experience.

frontend/src/i18n/locales/de/falukant.json

@@ -1353,6 +1353,20 @@
             "voteError": "Fehler beim Abgeben der Stimme",
             "voteAllError": "Fehler beim Abgeben der Stimmen",
             "applyError": "Bewerbung konnte nicht eingereicht werden.",
+            "benefits": {
+                "daily_salary": "Tagesamtshonorar (einmal pro Tag): ca. {amount}",
+                "tax_exemption": "Steuerbefreiung: {regions}",
+                "tax_exemption_all": "Steuerbefreiung: alle Regionsebenen",
+                "generic": "Vorteil ({code})"
+            },
+            "regionLevels": {
+                "city": "Stadt",
+                "county": "Landkreis",
+                "shire": "Grafschaft",
+                "markgrave": "Markgrafschaft",
+                "duchy": "Herzogtum",
+                "country": "Land"
+            },
             "current": {
                 "office": "Amt",
                 "region": "Region",