feat(bisaya-course): enhance phase 4 didactics with new learning goals and speaking prompts

- Expanded the BISAYA_PHASE4_DIDACTICS by adding new learning goals, core patterns, speaking prompts, and practical tasks to improve language acquisition.
- Updated the course content generation scripts to incorporate the new lesson structures and ensure alignment with the latest didactic updates.
- Enhanced the logic for generating exercises based on lesson types, introducing additional situational and speaking exercises for advanced lessons.

backend/scripts/create-german-for-bisaya-course-content.js

@@ -285,13 +285,24 @@ function generateExercisesFromDidactics(lesson) {
   const pool = getLessonPatternPool(didactics);
 
   if (lesson.lessonType === 'conversation') {
-    return [
+    const exercises = [
       buildChoiceExercise(lesson, didactics, patternA, pool, 0),
       buildGapExercise(lesson.title, patternA),
       buildSentenceExercise(lesson.title, patternB),
       buildSituationalExercise(lesson.title, didactics, patternA),
       buildSpeakingExercise(lesson.title, didactics, patternB)
     ].filter(Boolean);
+
+    // Ab Alltag/Stabilisierung konsequent mehr produktive Leistung verlangen.
+    if (Number(lesson.lessonNumber) >= 91) {
+      const extraSituational = buildSituationalExercise(lesson.title, didactics, patternB);
+      if (extraSituational) exercises.push(extraSituational);
+    }
+    if (Number(lesson.lessonNumber) >= 121) {
+      const extraSpeaking = buildSpeakingExercise(lesson.title, didactics, patternA);
+      if (extraSpeaking) exercises.push(extraSpeaking);
+    }
+    return exercises;
   }
 
   if (lesson.lessonType === 'grammar') {
@@ -305,7 +316,7 @@ function generateExercisesFromDidactics(lesson) {
   }
 
   if (lesson.lessonType === 'review' || lesson.didacticMode === 'intensive_review') {
-    return [
+    const exercises = [
       buildChoiceExercise(lesson, didactics, patternA, pool, 0),
       buildChoiceExercise(lesson, didactics, patternB, pool, 1),
       buildGapExercise(lesson.title, patternA),
@@ -313,6 +324,16 @@ function generateExercisesFromDidactics(lesson) {
       buildSituationalExercise(lesson.title, didactics, patternA),
       buildSpeakingExercise(lesson.title, didactics, patternB)
     ].filter(Boolean);
+
+    if (Number(lesson.lessonNumber) >= 91) {
+      const extraSpeaking = buildSpeakingExercise(lesson.title, didactics, patternA);
+      if (extraSpeaking) exercises.push(extraSpeaking);
+    }
+    if (String(lesson.title || '').toLowerCase().includes('checkpoint')) {
+      const extraSituational = buildSituationalExercise(lesson.title, didactics, patternB);
+      if (extraSituational) exercises.push(extraSituational);
+    }
+    return exercises;
   }
 
   if (lesson.lessonType === 'culture') {