Refactor vocabulary search functionality in VocabService and update UI components

- Modified the searchVocabs method in VocabService to consolidate search parameters into a single query term for improved flexibility.
- Updated VocabSearchDialog to replace separate input fields for mother tongue and learning language with a unified search term input.
- Adjusted button logic to enable search only when a term is provided, enhancing user experience.
- Added new translations for the search term in both German and English locales to support the updated UI.

backend/services/vocabService.js

@@ -408,20 +408,23 @@ export default class VocabService {
     return { languageId: access.id, isOwner: access.isOwner, vocabs: rows };
   }
 
-  async searchVocabs(hashedUserId, languageId, { learning = '', motherTongue = '' } = {}) {
+  async searchVocabs(hashedUserId, languageId, { q = '', learning = '', motherTongue = '' } = {}) {
     const user = await this._getUserByHashedId(hashedUserId);
     const access = await this._getLanguageAccess(user.id, languageId);
 
+    const query = typeof q === 'string' ? q.trim() : '';
+    // Abwärtskompatibel: falls alte Parameter genutzt werden, zusammenfassen
     const learningTerm = typeof learning === 'string' ? learning.trim() : '';
     const motherTerm = typeof motherTongue === 'string' ? motherTongue.trim() : '';
-    if (!learningTerm && !motherTerm) {
+    const effective = query || learningTerm || motherTerm;
+
+    if (!effective) {
       const err = new Error('Missing search term');
       err.status = 400;
       throw err;
     }
 
-    const learningLike = learningTerm ? `%${learningTerm}%` : null;
-    const motherLike = motherTerm ? `%${motherTerm}%` : null;
+    const like = `%${effective}%`;
 
     const rows = await sequelize.query(
       `
@@ -436,16 +439,14 @@ export default class VocabService {
       JOIN community.vocab_lexeme l1 ON l1.id = cl.learning_lexeme_id
       JOIN community.vocab_lexeme l2 ON l2.id = cl.reference_lexeme_id
       WHERE c.language_id = :languageId
-        AND (:learningLike IS NULL OR l1.text ILIKE :learningLike)
-        AND (:motherLike IS NULL OR l2.text ILIKE :motherLike)
+        AND (l1.text ILIKE :like OR l2.text ILIKE :like)
       ORDER BY l2.text ASC, l1.text ASC, c.title ASC
       LIMIT 200
       `,
       {
         replacements: {
           languageId: access.id,
-          learningLike,
-          motherLike,
+          like,
         },
         type: sequelize.QueryTypes.SELECT,
       }