refactor(VocabPracticeDialog): replace hard-coded consecutive correct threshold with constant

- Introduced a constant `HARD_REQUIRED_CONSECUTIVE_CORRECT` to define the required number of consecutive correct answers for hard vocabulary items, improving code maintainability and readability.
- Updated relevant methods to utilize the new constant, ensuring consistent behavior across the component.

frontend/src/dialogues/socialnetwork/VocabPracticeDialog.vue

@@ -159,6 +159,7 @@ import apiClient from '@/utils/axios.js';
 
 const PRACTICE_MIN_EXPOSURES = 3;
 const SRS_SESSION_STORAGE_VERSION = 2;
+const HARD_REQUIRED_CONSECUTIVE_CORRECT = 5;
 
 export default {
   name: 'VocabPracticeDialog',
@@ -303,10 +304,9 @@ export default {
       return this.pool.filter((item) => Boolean(this.hardVocabMap[this.getHardKey(item)]));
     },
     hardRemainingCount() {
-      const requiredConsecutiveCorrect = 2;
       return this.hardPoolItems.filter((item) => {
         const key = this.getHardKey(item);
-        return (Number(this.hardMasteryByKey[key]) || 0) < requiredConsecutiveCorrect;
+        return (Number(this.hardMasteryByKey[key]) || 0) < HARD_REQUIRED_CONSECUTIVE_CORRECT;
       }).length;
     }
   },
@@ -782,10 +782,9 @@ export default {
         return items.find((it) => it.id === nextId) || null;
       }
       if (this.hardPhaseActive) {
-        const requiredConsecutiveCorrect = 2;
         const hardItems = this.hardPoolItems.filter((item) => {
           const key = this.getHardKey(item);
-          return (Number(this.hardMasteryByKey[key]) || 0) < requiredConsecutiveCorrect;
+          return (Number(this.hardMasteryByKey[key]) || 0) < HARD_REQUIRED_CONSECUTIVE_CORRECT;
         });
         if (hardItems.length === 0) {
           this.hardPhaseActive = false;
@@ -939,7 +938,7 @@ export default {
         if (this.hardPhaseActive && this.current) {
           const key = this.getHardKey(this.current);
           this.hardMasteryByKey[key] = Math.max(0, Number(this.hardMasteryByKey[key]) || 0) + 1;
-          if ((Number(this.hardMasteryByKey[key]) || 0) >= 2 && this.hardVocabMap[key]) {
+          if ((Number(this.hardMasteryByKey[key]) || 0) >= HARD_REQUIRED_CONSECUTIVE_CORRECT && this.hardVocabMap[key]) {
             const next = { ...this.hardVocabMap };
             delete next[key];
             this.hardVocabMap = next;