refactor(vocab): improve text normalization consistency in VocabService and VocabLessonView

- Enhanced text normalization methods in both VocabService and VocabLessonView to include an additional trim operation, ensuring leading and trailing spaces are removed.
- This change improves the consistency and accuracy of text handling across the application, contributing to better user input processing.

backend/services/vocabService.js

@@ -346,7 +346,8 @@ export default class VocabService {
       .trim()
       .toLowerCase()
       .replace(/[\p{P}]+/gu, ' ')
-      .replace(/\s+/g, ' ');
+      .replace(/\s+/g, ' ')
+      .trim();
   }
 
   _parseExercisePayload(value) {

frontend/src/views/social/VocabLessonView.vue

@@ -2705,7 +2705,8 @@ export default {
         .trim()
         .toLowerCase()
         .replace(/[\p{P}]+/gu, ' ')
-        .replace(/\s+/g, ' ');
+        .replace(/\s+/g, ' ')
+        .trim();
     },
     normalizeVocab(s) {
       return this.normalizeComparableText(s);