feat(vocab): enrich core patterns with glosses in VocabService and VocabLessonView

- Implemented a new method in VocabService to enhance core patterns with glosses derived from extracted vocabulary, improving the clarity of vocabulary entries.
- Updated the VocabLessonView to utilize the enriched core patterns, ensuring that glosses are displayed alongside vocabulary targets for better user comprehension.
- Refactored vocabulary preparation logic to integrate glosses seamlessly, enhancing the overall user experience during vocabulary lessons.

frontend/src/views/social/VocabLessonView.vue

@@ -948,7 +948,18 @@ export default {
     },
     prepItems() {
       if (this.normalizedCorePatterns.length > 0) {
-        return this.normalizedCorePatterns;
+        const glossByReference = new Map(
+          (this.importantVocab || [])
+            .map((item) => [String(item?.reference || '').trim().toLowerCase(), String(item?.learning || '').trim()])
+            .filter(([reference, learning]) => reference && learning)
+        );
+        return this.normalizedCorePatterns.map((item) => {
+          if (item.gloss) {
+            return item;
+          }
+          const gloss = glossByReference.get(String(item.target || '').trim().toLowerCase()) || '';
+          return gloss ? { ...item, gloss } : item;
+        });
       }
       return (this.importantVocab || [])
         .map((item) => ({