feat(VocabPracticeDialog): implement immediate retry feature for incorrect answers

- Added a `pendingRetry` property to manage immediate retries after incorrect answers, enhancing user experience during vocabulary practice.
- Updated logic to handle retries, allowing users to quickly attempt the last question again with the correct direction.
- Ensured that the retry state is reset appropriately after correct answers or when skipping questions, maintaining clarity in the training flow.

frontend/src/dialogues/socialnetwork/VocabPracticeDialog.vue

@@ -178,6 +178,7 @@ export default {
       // current question
       current: null, // { id, learning, reference }
       direction: 'L2R', // L2R: learning->reference, R2L: reference->learning
+      pendingRetry: null, // { id, direction } for immediate retry after wrong answers
       acceptableAnswers: [],
       submittedAnswer: '',
       lastWrongReview: null,
@@ -378,6 +379,7 @@ export default {
       this.perId = {};
       this.lastIds = [];
       this.lastWrongReview = null;
+      this.pendingRetry = null;
       this.pool = [];
       this.locked = false;
       this.resetQuestion();
@@ -659,6 +661,13 @@ export default {
         if (!nextId) return null;
         return items.find((it) => it.id === nextId) || null;
       }
+      if (this.pendingRetry?.id) {
+        const retryItem = items.find((it) => it.id === this.pendingRetry.id);
+        if (retryItem) {
+          return retryItem;
+        }
+        this.pendingRetry = null;
+      }
       const recent = new Set(this.lastIds);
       const underexposed = items
         .map((item) => {
@@ -749,6 +758,7 @@ export default {
       if (isCorrect) {
         this.correctCount += 1;
         this.lastWrongReview = null;
+        this.pendingRetry = null;
       } else {
         this.wrongCount += 1;
         const answers = this.visibleCorrectAnswers.length > 0
@@ -759,6 +769,12 @@ export default {
           submittedAnswer: this.submittedAnswer,
           answers
         };
+        if (!this.srsMode && this.current?.id) {
+          this.pendingRetry = {
+            id: this.current.id,
+            direction: this.direction
+          };
+        }
       }
       if (!this.srsMode) {
         this.reportSrsReview(isCorrect);
@@ -836,6 +852,7 @@ export default {
       }
     },
     skip() {
+      this.pendingRetry = null;
       this.next();
     },
     next() {
@@ -851,7 +868,11 @@ export default {
         this.resetQuestion();
         return;
       }
+      const retryDirection = this.pendingRetry?.direction || null;
       this.resetQuestion();
+      if (retryDirection) {
+        this.direction = retryDirection;
+      }
       this.current = this.pickNextItem();
       if (!this.current) return;
       const prompt = this.currentPrompt;