feat(bisaya-course): add new lesson and update course creation logic

- Introduced a new lesson titled "Zahlen & Preise" to enhance the numerical curriculum in Bisaya.
- Updated the course creation logic to check for existing "Familien"-Bisaya courses, ensuring idempotency in course creation.
- Enhanced the lesson didactics by mapping legacy titles to current lesson keys, improving data consistency.
- Adjusted the course generation script to limit Bisaya courses to German-speaking learners only, streamlining course offerings.

backend/scripts/update-bisaya-didactics.js

@@ -10,7 +10,12 @@ import { sequelize } from '../utils/sequelize.js';
 import VocabCourseLesson from '../models/community/vocab_course_lesson.js';
 import { getBisayaLessonPedagogy } from './bisaya-course-phase2-pedagogy.js';
 
-const LESSON_DIDACTICS = {
+/** Alte Kurstitel → aktueller Schlüssel in LESSON_DIDACTICS (bestehende Datenbanken). */
+export const LEGACY_DIDACTICS_TITLE_MAP = {
+  'Zahlen & Preise': 'Zahlen 1–20'
+};
+
+export const LESSON_DIDACTICS = {
   'Begrüßungen & Höflichkeit': {
     learningGoals: [
       'Einfache Begrüßungen verstehen und selbst verwenden.',
@@ -438,6 +443,14 @@ const LESSON_DIDACTICS = {
   }
 };
 
+function resolveDidacticsForLesson(lesson) {
+  const direct = LESSON_DIDACTICS[lesson.title];
+  if (direct) return direct;
+  const mappedTitle = LEGACY_DIDACTICS_TITLE_MAP[lesson.title];
+  if (mappedTitle) return LESSON_DIDACTICS[mappedTitle];
+  return null;
+}
+
 async function updateBisayaDidactics() {
   await sequelize.authenticate();
   const [bisayaLanguage] = await sequelize.query(
@@ -464,25 +477,29 @@ async function updateBisayaDidactics() {
   let updated = 0;
   for (const row of lessons) {
     const lesson = await VocabCourseLesson.findByPk(row.id);
-    const didactics = LESSON_DIDACTICS[lesson.title];
+    const didactics = resolveDidacticsForLesson(lesson);
     const pedagogy = getBisayaLessonPedagogy(lesson.lessonNumber);
     if (!didactics && !pedagogy) continue;
-    const normalizedDidactics = didactics || {};
 
-    await lesson.update({
-      learningGoals: normalizedDidactics.learningGoals || [],
-      corePatterns: normalizedDidactics.corePatterns || [],
-      grammarFocus: normalizedDidactics.grammarFocus || [],
-      speakingPrompts: normalizedDidactics.speakingPrompts || [],
-      practicalTasks: normalizedDidactics.practicalTasks || [],
-      didacticMode: pedagogy?.didacticMode || null,
-      phaseLabel: pedagogy?.phaseLabel || null,
-      blockNumber: pedagogy?.blockNumber ?? null,
-      difficultyWeight: pedagogy?.difficultyWeight ?? null,
-      newUnitTarget: pedagogy?.newUnitTarget ?? null,
-      reviewWeight: pedagogy?.reviewWeight ?? null,
-      isIntensiveReview: Boolean(pedagogy?.isIntensiveReview)
-    });
+    const patch = {};
+    if (didactics) {
+      patch.learningGoals = didactics.learningGoals || [];
+      patch.corePatterns = didactics.corePatterns || [];
+      patch.grammarFocus = didactics.grammarFocus || [];
+      patch.speakingPrompts = didactics.speakingPrompts || [];
+      patch.practicalTasks = didactics.practicalTasks || [];
+    }
+    if (pedagogy) {
+      patch.didacticMode = pedagogy.didacticMode || null;
+      patch.phaseLabel = pedagogy.phaseLabel || null;
+      patch.blockNumber = pedagogy.blockNumber ?? null;
+      patch.difficultyWeight = pedagogy.difficultyWeight ?? null;
+      patch.newUnitTarget = pedagogy.newUnitTarget ?? null;
+      patch.reviewWeight = pedagogy.reviewWeight ?? null;
+      patch.isIntensiveReview = Boolean(pedagogy.isIntensiveReview);
+    }
+
+    await lesson.update(patch);
     updated++;
     console.log(`✅ Didaktik aktualisiert: Lektion ${lesson.lessonNumber} - ${lesson.title}`);
   }