feat(VocabService, VocabPracticeDialog, VocabLessonView): enhance vocabulary training logic and UI feedback

- Introduced methods for improved text analysis and validation in VocabService, including `_wordCount` and `_looksLikeFragmentMismatch`, to better assess learning and reference pairs.
- Updated VocabPracticeDialog to display submitted answers and correct solutions, enhancing user feedback during practice sessions.
- Enhanced VocabLessonView to ensure only trainable vocabulary pairs are processed, improving the quality of vocabulary training.
- Added localization entries for new UI elements in both English and German, ensuring clarity in user interactions.

backend/services/vocabService.js

@@ -92,9 +92,35 @@ export default class VocabService {
       return false;
     }
 
+    if (this._looksLikeFragmentMismatch(learning, reference)) {
+      return false;
+    }
+
     return !this._isInstructionLikeText(learning) && !this._isInstructionLikeText(reference);
   }
 
+  _wordCount(value) {
+    return String(value || '')
+      .trim()
+      .replace(/[\p{P}\p{S}]+/gu, ' ')
+      .split(/\s+/)
+      .filter(Boolean)
+      .length;
+  }
+
+  _looksLikeFragmentMismatch(left, right) {
+    const leftWords = this._wordCount(left);
+    const rightWords = this._wordCount(right);
+    const leftText = String(left || '').trim();
+    const rightText = String(right || '').trim();
+    const leftLooksSentence = leftWords >= 3 || /[?!.].+\S/.test(leftText);
+    const rightLooksSentence = rightWords >= 3 || /[?!.].+\S/.test(rightText);
+    const leftLooksShortFragment = leftWords <= 1 && leftText.length <= 12;
+    const rightLooksShortFragment = rightWords <= 1 && rightText.length <= 12;
+
+    return (leftLooksShortFragment && rightLooksSentence) || (rightLooksShortFragment && leftLooksSentence);
+  }
+
   _calculateSrsSchedule(item, { correct, rating = null } = {}) {
     const now = new Date();
     const previousStage = Math.max(0, Number(item?.stage) || 0);

frontend/src/dialogues/socialnetwork/VocabPracticeDialog.vue

@@ -42,15 +42,20 @@
             <div v-if="lastCorrect">{{ $t('socialnetwork.vocab.practice.correct') }}</div>
             <div v-else>
               {{ $t('socialnetwork.vocab.practice.wrong') }}
-              <div class="answers">
-                <div class="answersTitle">{{ $t('socialnetwork.vocab.practice.acceptable') }}</div>
-                <ul>
-                  <li v-for="a in acceptableAnswers" :key="a">{{ a }}</li>
-                </ul>
-              </div>
             </div>
           </div>
 
+          <div v-if="answered && !lastCorrect" class="solution-card">
+            <div v-if="submittedAnswer" class="submitted-answer">
+              <span>{{ $t('socialnetwork.vocab.practice.yourAnswer') }}</span>
+              <strong>{{ submittedAnswer }}</strong>
+            </div>
+            <div class="answersTitle">{{ $t('socialnetwork.vocab.practice.correctSolutions') }}</div>
+            <ul>
+              <li v-for="a in visibleCorrectAnswers" :key="a">{{ a }}</li>
+            </ul>
+          </div>
+
           <div v-if="showSrsRatingButtons" class="srs-rating">
             <div class="srs-rating__title">{{ $t('socialnetwork.vocab.practice.srsRateTitle') }}</div>
             <button
@@ -169,6 +174,7 @@ export default {
       current: null, // { id, learning, reference }
       direction: 'L2R', // L2R: learning->reference, R2L: reference->learning
       acceptableAnswers: [],
+      submittedAnswer: '',
       choiceOptions: [],
       typedAnswer: '',
       answered: false,
@@ -211,6 +217,17 @@ export default {
     showSrsRatingButtons() {
       return this.srsMode && this.answered && !this.locked;
     },
+    visibleCorrectAnswers() {
+      const answers = Array.isArray(this.acceptableAnswers) ? this.acceptableAnswers.filter(Boolean) : [];
+      if (answers.length > 0) {
+        return answers;
+      }
+      if (!this.current) {
+        return [];
+      }
+      const fallback = this.direction === 'L2R' ? this.current.reference : this.current.learning;
+      return this.expandAnswerVariants(fallback);
+    },
     srsRatingOptions() {
       if (!this.answered) {
         return [];
@@ -429,8 +446,31 @@ export default {
       if (!learning || !reference || this.normalize(learning) === this.normalize(reference)) {
         return false;
       }
+      if (this.looksLikeFragmentMismatch(learning, reference)) {
+        return false;
+      }
       return !this.isInstructionLikeText(learning) && !this.isInstructionLikeText(reference);
     },
+    wordCount(value) {
+      return String(value || '')
+        .trim()
+        .replace(/[\p{P}\p{S}]+/gu, ' ')
+        .split(/\s+/)
+        .filter(Boolean)
+        .length;
+    },
+    looksLikeFragmentMismatch(left, right) {
+      const leftWords = this.wordCount(left);
+      const rightWords = this.wordCount(right);
+      const leftText = String(left || '').trim();
+      const rightText = String(right || '').trim();
+      const leftLooksSentence = leftWords >= 3 || /[?!.].+\S/.test(leftText);
+      const rightLooksSentence = rightWords >= 3 || /[?!.].+\S/.test(rightText);
+      const leftLooksShortFragment = leftWords <= 1 && leftText.length <= 12;
+      const rightLooksShortFragment = rightWords <= 1 && rightText.length <= 12;
+
+      return (leftLooksShortFragment && rightLooksSentence) || (rightLooksShortFragment && leftLooksSentence);
+    },
     normalizePool(items = []) {
       const seen = new Set();
       return (Array.isArray(items) ? items : [])
@@ -458,6 +498,7 @@ export default {
       this.current = null;
       this.direction = this.openParams?.lessonId ? 'L2R' : (Math.random() < 0.5 ? 'L2R' : 'R2L');
       this.acceptableAnswers = [];
+      this.submittedAnswer = '';
       this.choiceOptions = [];
       this.typedAnswer = '';
       this.answered = false;
@@ -473,6 +514,7 @@ export default {
       this.answered = false;
       this.lastCorrect = false;
       this.typedAnswer = '';
+      this.submittedAnswer = '';
 
       if (!this.pool || this.pool.length === 0) return;
 
@@ -746,6 +788,7 @@ export default {
     },
     submitChoice(opt) {
       if (this.locked) return;
+      this.submittedAnswer = String(opt || '').trim();
       const ok = this.acceptableAnswers.map(this.normalize).includes(this.normalize(opt));
       this.markResult(ok);
       this.playSound(ok);
@@ -760,6 +803,7 @@ export default {
     },
     submitTyped() {
       if (this.locked) return;
+      this.submittedAnswer = String(this.typedAnswer || '').trim();
       const ans = this.normalize(this.typedAnswer);
       const ok = this.acceptableAnswers.map(this.normalize).includes(ans);
       this.markResult(ok);
@@ -927,6 +971,25 @@ export default {
   background: #ffecec;
   border-color: #d33;
 }
+.solution-card {
+  margin: 0 0 12px;
+  padding: 12px;
+  border: 1px solid #d33;
+  background: #fff8f8;
+}
+.solution-card ul {
+  margin: 6px 0 0;
+  padding-left: 20px;
+}
+.submitted-answer {
+  display: grid;
+  gap: 3px;
+  margin-bottom: 10px;
+  color: #5f554e;
+}
+.submitted-answer strong {
+  color: #2b2520;
+}
 .answersTitle {
   margin-top: 6px;
   font-weight: bold;

frontend/src/i18n/locales/de/socialnetwork.json

@@ -451,6 +451,8 @@
                 "correct": "Richtig!",
                 "wrong": "Falsch.",
                 "acceptable": "Mögliche richtige Übersetzungen:",
+                "correctSolutions": "Richtige Antwort:",
+                "yourAnswer": "Deine Antwort:",
                 "stats": "Statistik",
                 "dueToday": "Heute fällig",
                 "done": "Erledigt",

frontend/src/i18n/locales/en/socialnetwork.json

@@ -451,6 +451,8 @@
                 "correct": "Correct!",
                 "wrong": "Wrong.",
                 "acceptable": "Acceptable answers:",
+                "correctSolutions": "Correct answer:",
+                "yourAnswer": "Your answer:",
                 "stats": "Stats",
                 "dueToday": "Due today",
                 "done": "Done",

frontend/src/views/social/VocabLessonView.vue

@@ -1452,7 +1452,7 @@ export default {
         const oriented = orientPair(entry?.learning, entry?.reference);
         const reference = String(oriented.reference || '').trim();
         const learning = String(oriented.learning || '').trim();
-        if (!reference) return;
+        if (!this.isTrainableLessonVocabPair(learning, reference)) return;
         const key = this.normalizeLessonVocabTerm(reference);
         if (!vocabByReference.has(key)) {
           const variants = new Set();
@@ -1523,7 +1523,7 @@ export default {
       return { from, to, page, pages: totalPages, total: n };
     },
     trainableLessonVocab() {
-      return this.lessonVocab.filter((entry) => entry.learning && entry.reference && entry.learning !== entry.reference);
+      return this.lessonVocab.filter((entry) => this.isTrainableLessonVocabPair(entry.learning, entry.reference));
     },
     lessonDidactics() {
       return this.lesson?.didactics || {
@@ -1610,7 +1610,7 @@ export default {
         const oriented = orientPair(target, gloss);
         const t = String(oriented.target || '').trim();
         const g = String(oriented.gloss || '').trim();
-        if (!t || !g) return;
+        if (!this.isTrainableLessonVocabPair(g, t)) return;
         const key = `${this.normalizeLessonVocabTerm(t)}|${this.normalizeLessonVocabTerm(g)}`;
         if (seen.has(key)) return;
         seen.add(key);
@@ -2125,6 +2125,34 @@ export default {
         .replace(/^[.,!?;:]+|[.,!?;:]+$/g, '')
         .trim();
     },
+    lessonVocabWordCount(value) {
+      return String(value || '')
+        .trim()
+        .replace(/[\p{P}\p{S}]+/gu, ' ')
+        .split(/\s+/)
+        .filter(Boolean)
+        .length;
+    },
+    looksLikeLessonVocabFragmentMismatch(left, right) {
+      const leftWords = this.lessonVocabWordCount(left);
+      const rightWords = this.lessonVocabWordCount(right);
+      const leftText = String(left || '').trim();
+      const rightText = String(right || '').trim();
+      const leftLooksSentence = leftWords >= 3 || /[?!.].+\S/.test(leftText);
+      const rightLooksSentence = rightWords >= 3 || /[?!.].+\S/.test(rightText);
+      const leftLooksShortFragment = leftWords <= 1 && leftText.length <= 12;
+      const rightLooksShortFragment = rightWords <= 1 && rightText.length <= 12;
+
+      return (leftLooksShortFragment && rightLooksSentence) || (rightLooksShortFragment && leftLooksSentence);
+    },
+    isTrainableLessonVocabPair(learning, reference) {
+      const l = String(learning || '').trim();
+      const r = String(reference || '').trim();
+      if (!l || !r || this.normalizeLessonVocabTerm(l) === this.normalizeLessonVocabTerm(r)) {
+        return false;
+      }
+      return !this.looksLikeLessonVocabFragmentMismatch(l, r);
+    },
     normalizeCorePatternEntry(p) {
       if (p && typeof p === 'object' && p.target) {
         return {