Add search functionality for vocabulary in VocabController and VocabService

- Implemented a new searchVocabs method in VocabService to allow users to search for vocabulary based on learning and mother tongue terms.
- Updated VocabController to include the searchVocabs method wrapped with user authentication.
- Added a new route in vocabRouter for searching vocabulary by language ID.
- Enhanced VocabChapterView and VocabLanguageView components to include a button for opening the search dialog.
- Added translations for search-related terms in both German and English locales, improving user accessibility.

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

@@ -308,6 +308,16 @@
                 "stats": "Statistik",
                 "success": "Erfolg",
                 "fail": "Misserfolg"
+            },
+            "search": {
+                "open": "Suche",
+                "title": "Vokabeln suchen",
+                "motherTongue": "Muttersprache",
+                "learningLanguage": "Lernsprache",
+                "lesson": "Lektion",
+                "search": "Suchen",
+                "noResults": "Keine Treffer.",
+                "error": "Suche fehlgeschlagen."
             }
         }
     }