feat(admin): add user vocab course management functionality

- Implemented `getUserVocabCourses` and `getVocabCourseForAdmin` methods in `AdminController` to allow admins to retrieve enrolled vocab courses for users and specific course details, respectively.
- Updated `adminRouter` to include new routes for accessing user vocab courses and course details.
- Enhanced `AdminService` with methods to list user-enrolled vocab courses and retrieve course information with lessons, ensuring proper access control.
- Improved `VocabService` to support the new functionalities, including attaching language names to course data.
- Updated UI components in `UsersView` to reflect changes, including error handling and loading states for course retrieval, along with localization updates for new features.

frontend/src/i18n/locales/ceb/admin.json

@@ -23,8 +23,8 @@
     },
     "vocabLessonReset": {
       "title": "Kurso sa pinulongan: pag-uswag sa leksiyon",
-      "intro": "Tangtanga ang pag-uswag, mga resulta sa ehersisyo ug natipig nga kahimtang sa usa ka leksiyon lamang (dili ang tibuok kurso). Makita ra ang mga kurso nga makita sa imong admin account (publiko o imoha).",
-      "loadCourses": "Ikarga ang mga kurso",
+      "intro": "Tangtanga ang pag-uswag, mga resulta sa ehersisyo ug natipig nga kahimtang sa usa ka leksiyon lamang (dili ang tibuok kurso). Makita ra ang mga kurso nga na-enroll niini nga tiggamit.",
+      "loadCourses": "Ikarga ang na-enroll nga mga kurso",
       "selectCourse": "Kurso",
       "selectLesson": "Leksiyon",
       "reset": "I-reset ang leksiyon niining user",
@@ -32,7 +32,8 @@
       "success": "Na-reset na ang pag-uswag sa leksiyon.",
       "error": "Dili ma-reset.",
       "pickUserFirst": "Una pagpili ug user.",
-      "noCourses": "Walay nakarga nga kurso o walay makita nga kurso.",
+      "noEnrolledCourses": "Kini nga tiggamit wala na-enroll sa bisan unsang kurso sa pinulongan.",
+      "loadCoursesError": "Dili makarga ang lista sa mga kurso.",
       "loadingLessons": "Nagkarga sa mga leksiyon …"
     },
     "rights": {

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

@@ -32,8 +32,8 @@
         },
         "vocabLessonReset": {
             "title": "Sprachkurs: Lektionsfortschritt",
-            "intro": "Fortschritt, Übungsergebnisse und gespeicherter Lektionszustand für eine einzelne Lektion löschen (nicht der ganze Kurs). Es werden nur Kurse gelistet, die du als Admin sehen kannst (öffentlich oder eigene).",
-            "loadCourses": "Kurse laden",
+            "intro": "Fortschritt, Übungsergebnisse und gespeicherter Lektionszustand für eine einzelne Lektion löschen (nicht der ganze Kurs). Es werden nur Sprachkurse gelistet, in die dieser Benutzer eingeschrieben ist.",
+            "loadCourses": "Eingeschriebene Kurse laden",
             "selectCourse": "Kurs",
             "selectLesson": "Lektion",
             "reset": "Lektion für diesen Nutzer zurücksetzen",
@@ -41,7 +41,8 @@
             "success": "Lektionsfortschritt wurde zurückgesetzt.",
             "error": "Zurücksetzen fehlgeschlagen.",
             "pickUserFirst": "Zuerst einen Benutzer auswählen.",
-            "noCourses": "Keine Kurse geladen oder keine sichtbaren Kurse.",
+            "noEnrolledCourses": "Dieser Benutzer ist in keinem Sprachkurs eingeschrieben.",
+            "loadCoursesError": "Die Kursliste konnte nicht geladen werden.",
             "loadingLessons": "Lektionen werden geladen …"
         },
         "adultVerification": {

frontend/src/i18n/locales/en/admin.json

@@ -32,8 +32,8 @@
         },
         "vocabLessonReset": {
             "title": "Language course: lesson progress",
-            "intro": "Delete progress, exercise results and saved lesson state for a single lesson (not the whole course). Only courses you can see as this admin account are listed (public or your own).",
-            "loadCourses": "Load courses",
+            "intro": "Delete progress, exercise results and saved lesson state for a single lesson (not the whole course). Only language courses this user is enrolled in are listed.",
+            "loadCourses": "Load enrolled courses",
             "selectCourse": "Course",
             "selectLesson": "Lesson",
             "reset": "Reset lesson for this user",
@@ -41,7 +41,8 @@
             "success": "Lesson progress was reset.",
             "error": "Reset failed.",
             "pickUserFirst": "Select a user first.",
-            "noCourses": "No courses loaded or no visible courses.",
+            "noEnrolledCourses": "This user is not enrolled in any language course.",
+            "loadCoursesError": "Could not load the course list.",
             "loadingLessons": "Loading lessons…"
         },
         "adultVerification": {

frontend/src/i18n/locales/es/admin.json

@@ -32,8 +32,8 @@
         },
         "vocabLessonReset": {
             "title": "Curso de idiomas: progreso de lección",
-            "intro": "Elimina el progreso, los resultados de ejercicios y el estado guardado de una sola lección (no todo el curso). Solo se listan cursos visibles para tu cuenta de administración (públicos o propios).",
-            "loadCourses": "Cargar cursos",
+            "intro": "Elimina el progreso, los resultados de ejercicios y el estado guardado de una sola lección (no todo el curso). Solo aparecen los cursos de idiomas en los que está inscrito este usuario.",
+            "loadCourses": "Cargar cursos inscritos",
             "selectCourse": "Curso",
             "selectLesson": "Lección",
             "reset": "Restablecer lección para este usuario",
@@ -41,7 +41,8 @@
             "success": "Se restableció el progreso de la lección.",
             "error": "No se pudo restablecer.",
             "pickUserFirst": "Primero elige un usuario.",
-            "noCourses": "No hay cursos cargados o no hay cursos visibles.",
+            "noEnrolledCourses": "Este usuario no está inscrito en ningún curso de idiomas.",
+            "loadCoursesError": "No se pudo cargar la lista de cursos.",
             "loadingLessons": "Cargando lecciones…"
         },
         "adultVerification": {