feat(admin): add potential fathers retrieval for character management

- Implemented a new method in AdminService to fetch potential fathers for a given character based on existing relationships.
- Updated AdminController to expose this functionality via a new API endpoint.
- Enhanced adminRouter to include the route for retrieving potential fathers.
- Modified frontend components to allow selection of potential fathers during pregnancy and birth management.
- Updated internationalization files to include new translation keys related to father selection.

backend/services/vocabService.js

@@ -188,6 +188,149 @@ export default class VocabService {
     return [];
   }
 
+  _normalizeOptionalInteger(value) {
+    if (value === undefined || value === null || value === '') {
+      return null;
+    }
+    const parsed = Number(value);
+    return Number.isFinite(parsed) ? parsed : null;
+  }
+
+  _normalizeOptionalString(value) {
+    if (value === undefined || value === null) {
+      return null;
+    }
+    const trimmed = String(value).trim();
+    return trimmed || null;
+  }
+
+  _inferLessonPhaseLabel(plainLesson) {
+    if (plainLesson.phaseLabel) {
+      return plainLesson.phaseLabel;
+    }
+    const weekNumber = Number(plainLesson.weekNumber) || 0;
+    if (weekNumber > 0 && weekNumber <= 2) {
+      return 'quickstart';
+    }
+    if (weekNumber === 3) {
+      return 'daily_life';
+    }
+    if (weekNumber >= 4) {
+      return 'stabilization';
+    }
+    return 'quickstart';
+  }
+
+  _inferLessonDidacticMode(plainLesson) {
+    if (plainLesson.didacticMode) {
+      return plainLesson.didacticMode;
+    }
+    const lessonType = String(plainLesson.lessonType || '').toLowerCase();
+    const title = String(plainLesson.title || '').toLowerCase();
+    if (title.includes('abschluss') || title.includes('prüfung') || title.includes('test')) {
+      return 'checkpoint';
+    }
+    if (plainLesson.isIntensiveReview || lessonType === 'review' || lessonType === 'vocab_review' || title.includes('wiederholung')) {
+      return 'intensive_review';
+    }
+    if (lessonType === 'grammar') {
+      return 'pattern_drill';
+    }
+    if (lessonType === 'conversation' || lessonType === 'dialogue' || lessonType === 'phrases' || lessonType === 'survival') {
+      return 'guided_dialogue';
+    }
+    if (lessonType === 'culture') {
+      return 'real_life_scenario';
+    }
+    return 'core_input';
+  }
+
+  _inferLessonDifficultyWeight(plainLesson, didacticMode) {
+    if (plainLesson.difficultyWeight != null) {
+      return plainLesson.difficultyWeight;
+    }
+    switch (didacticMode) {
+      case 'pattern_drill':
+        return 3;
+      case 'guided_dialogue':
+      case 'real_life_scenario':
+        return 2;
+      case 'intensive_review':
+      case 'checkpoint':
+        return 2;
+      default:
+        return 1;
+    }
+  }
+
+  _inferLessonNewUnitTarget(plainLesson, didacticMode) {
+    if (plainLesson.newUnitTarget != null) {
+      return plainLesson.newUnitTarget;
+    }
+    switch (didacticMode) {
+      case 'core_input':
+        return 8;
+      case 'guided_dialogue':
+        return 5;
+      case 'pattern_drill':
+        return 4;
+      case 'real_life_scenario':
+        return 3;
+      case 'checkpoint':
+        return 2;
+      case 'intensive_review':
+        return 1;
+      default:
+        return 4;
+    }
+  }
+
+  _inferLessonReviewWeight(plainLesson, didacticMode) {
+    if (plainLesson.reviewWeight != null) {
+      return plainLesson.reviewWeight;
+    }
+    switch (didacticMode) {
+      case 'intensive_review':
+        return 90;
+      case 'checkpoint':
+        return 70;
+      case 'pattern_drill':
+        return 55;
+      case 'real_life_scenario':
+        return 45;
+      case 'guided_dialogue':
+        return 40;
+      default:
+        return 30;
+    }
+  }
+
+  _inferLessonBlockNumber(plainLesson) {
+    if (plainLesson.blockNumber != null) {
+      return plainLesson.blockNumber;
+    }
+    const weekNumber = Number(plainLesson.weekNumber) || 1;
+    return Math.max(1, Math.ceil(weekNumber / 2));
+  }
+
+  _buildLessonPedagogy(plainLesson) {
+    const didacticMode = this._inferLessonDidacticMode(plainLesson);
+    const phaseLabel = this._inferLessonPhaseLabel(plainLesson);
+    const isIntensiveReview = plainLesson.isIntensiveReview != null
+      ? Boolean(plainLesson.isIntensiveReview)
+      : didacticMode === 'intensive_review';
+
+    return {
+      didacticMode,
+      phaseLabel,
+      blockNumber: this._inferLessonBlockNumber(plainLesson),
+      difficultyWeight: this._inferLessonDifficultyWeight(plainLesson, didacticMode),
+      newUnitTarget: this._inferLessonNewUnitTarget(plainLesson, didacticMode),
+      reviewWeight: this._inferLessonReviewWeight(plainLesson, didacticMode),
+      isIntensiveReview
+    };
+  }
+
   _buildLessonDidactics(plainLesson) {
     const grammarExercises = Array.isArray(plainLesson.grammarExercises) ? plainLesson.grammarExercises : [];
     const grammarExplanations = [];
@@ -1020,6 +1163,11 @@ export default class VocabService {
       return a.lessonNumber - b.lessonNumber;
     });
 
+    courseData.lessons = courseData.lessons.map((lesson) => ({
+      ...lesson,
+      pedagogy: this._buildLessonPedagogy(lesson)
+    }));
+
     return courseData;
   }
 
@@ -1129,6 +1277,7 @@ export default class VocabService {
     }
     
     plainLesson.didactics = this._buildLessonDidactics(plainLesson);
+    plainLesson.pedagogy = this._buildLessonPedagogy(plainLesson);
     return plainLesson;
   }
 
@@ -1301,7 +1450,7 @@ export default class VocabService {
     return exercises.map(e => e.get({ plain: true }));
   }
 
-  async addLessonToCourse(hashedUserId, courseId, { chapterId, lessonNumber, title, description, weekNumber, dayNumber, lessonType, audioUrl, culturalNotes, learningGoals, corePatterns, grammarFocus, speakingPrompts, practicalTasks, targetMinutes, targetScorePercent, requiresReview }) {
+  async addLessonToCourse(hashedUserId, courseId, { chapterId, lessonNumber, title, description, weekNumber, dayNumber, lessonType, didacticMode, phaseLabel, blockNumber, difficultyWeight, newUnitTarget, reviewWeight, isIntensiveReview, audioUrl, culturalNotes, learningGoals, corePatterns, grammarFocus, speakingPrompts, practicalTasks, targetMinutes, targetScorePercent, requiresReview }) {
     const user = await this._getUserByHashedId(hashedUserId);
     const course = await VocabCourse.findByPk(courseId);
 
@@ -1343,6 +1492,13 @@ export default class VocabService {
       weekNumber: weekNumber ? Number(weekNumber) : null,
       dayNumber: dayNumber ? Number(dayNumber) : null,
       lessonType: lessonType || 'vocab',
+      didacticMode: this._normalizeOptionalString(didacticMode),
+      phaseLabel: this._normalizeOptionalString(phaseLabel),
+      blockNumber: this._normalizeOptionalInteger(blockNumber),
+      difficultyWeight: this._normalizeOptionalInteger(difficultyWeight),
+      newUnitTarget: this._normalizeOptionalInteger(newUnitTarget),
+      reviewWeight: this._normalizeOptionalInteger(reviewWeight),
+      isIntensiveReview: isIntensiveReview !== undefined ? Boolean(isIntensiveReview) : false,
       audioUrl: audioUrl || null,
       culturalNotes: culturalNotes || null,
       learningGoals: this._normalizeStringList(learningGoals),
@@ -1358,7 +1514,7 @@ export default class VocabService {
     return lesson.get({ plain: true });
   }
 
-  async updateLesson(hashedUserId, lessonId, { title, description, lessonNumber, weekNumber, dayNumber, lessonType, audioUrl, culturalNotes, learningGoals, corePatterns, grammarFocus, speakingPrompts, practicalTasks, targetMinutes, targetScorePercent, requiresReview }) {
+  async updateLesson(hashedUserId, lessonId, { title, description, lessonNumber, weekNumber, dayNumber, lessonType, didacticMode, phaseLabel, blockNumber, difficultyWeight, newUnitTarget, reviewWeight, isIntensiveReview, audioUrl, culturalNotes, learningGoals, corePatterns, grammarFocus, speakingPrompts, practicalTasks, targetMinutes, targetScorePercent, requiresReview }) {
     const user = await this._getUserByHashedId(hashedUserId);
     const lesson = await VocabCourseLesson.findByPk(lessonId, {
       include: [{ model: VocabCourse, as: 'course' }]
@@ -1383,6 +1539,13 @@ export default class VocabService {
     if (weekNumber !== undefined) updates.weekNumber = weekNumber ? Number(weekNumber) : null;
     if (dayNumber !== undefined) updates.dayNumber = dayNumber ? Number(dayNumber) : null;
     if (lessonType !== undefined) updates.lessonType = lessonType;
+    if (didacticMode !== undefined) updates.didacticMode = this._normalizeOptionalString(didacticMode);
+    if (phaseLabel !== undefined) updates.phaseLabel = this._normalizeOptionalString(phaseLabel);
+    if (blockNumber !== undefined) updates.blockNumber = this._normalizeOptionalInteger(blockNumber);
+    if (difficultyWeight !== undefined) updates.difficultyWeight = this._normalizeOptionalInteger(difficultyWeight);
+    if (newUnitTarget !== undefined) updates.newUnitTarget = this._normalizeOptionalInteger(newUnitTarget);
+    if (reviewWeight !== undefined) updates.reviewWeight = this._normalizeOptionalInteger(reviewWeight);
+    if (isIntensiveReview !== undefined) updates.isIntensiveReview = Boolean(isIntensiveReview);
     if (audioUrl !== undefined) updates.audioUrl = audioUrl;
     if (culturalNotes !== undefined) updates.culturalNotes = culturalNotes;
     if (learningGoals !== undefined) updates.learningGoals = this._normalizeStringList(learningGoals);