Subjects per grade (math, calculus, geometry, stats, discrete), 5 new textbooks, 202 new islands, long islands split, hand-written figures and lesson texts for the new books

- content.Subject + Unit.subject, /api/home?subject=, tutor grounded in the chosen book
- 5 new books ingested; ~1150 hand-written questions, islands named by hand
- node_split: islands over 7 lessons split into parts of <=6 (lesson ids and progress kept)
- Lesson.figures hand-authored and visually checked for 653 lessons of the new books;
  gen_lesson_figures got --subject and survives network errors
- seed files re-exported

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

content/tests_lesson_texts.py

@@ -12,7 +12,7 @@ from rag.models import LessonChunk
 
 def _curriculum(blurb='', example='', steps=None):
     return json.dumps({'grades': [{'title': 'پایه آزمون', 'units': [{
-        'title': 'فصل ۱', 'blurb': blurb, 'nodes': [{'title': 'جزیره', 'lessons': [
+        'subject': 'ریاضی', 'title': 'فصل ۱', 'blurb': blurb, 'nodes': [{'title': 'جزیره', 'lessons': [
             {'title': 'درس', 'introText': 'توضیح', 'example': example, 'steps': steps or []},
         ]}],
     }]}]}).encode()