Add course retrieval by share code feature and enhance course search functionality

- Implemented a new endpoint in VocabController to retrieve courses using a share code.
- Updated VocabService to include logic for validating share codes and checking course access permissions.
- Enhanced course listing functionality with search and language filtering options in the frontend.
- Added a dialog for users to input share codes and search for courses, improving user experience.
- Updated internationalization files to include new strings for share code functionality and search features.

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

@@ -347,7 +347,13 @@
                 "confirmDelete": "Lektion wirklich löschen?",
                 "titleLabel": "Titel",
                 "descriptionLabel": "Beschreibung",
-                "languageLabel": "Sprache"
+                "languageLabel": "Sprache",
+                "findByCode": "Kurs per Code finden",
+                "shareCode": "Share-Code",
+                "searchPlaceholder": "Kurs suchen...",
+                "allLanguages": "Alle Sprachen",
+                "invalidCode": "Ungültiger Code",
+                "courseNotFound": "Kurs nicht gefunden"
             }
         }
     }

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

@@ -347,7 +347,13 @@
                 "confirmDelete": "Really delete lesson?",
                 "titleLabel": "Title",
                 "descriptionLabel": "Description",
-                "languageLabel": "Language"
+                "languageLabel": "Language",
+                "findByCode": "Find Course by Code",
+                "shareCode": "Share Code",
+                "searchPlaceholder": "Search courses...",
+                "allLanguages": "All Languages",
+                "invalidCode": "Invalid code",
+                "courseNotFound": "Course not found"
             }
         }
     }