Remove the guest system entirely: no is_guest/device_id, no guest throttles, phone login is the only way in

accounts.0008 drops the columns and refuses to run while guest rows exist.
Docs describe the current state; tests that only proved guest behaviour are gone.

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

tools/loadtest/mkusers.py

@@ -1,5 +1,5 @@
 # Run with: manage.py shell -c "exec(open('tools/loadtest/mkusers.py').read())"   env: LT_N, LT_PREFIX, LT_SEED
-# Creates N non-guest test users (fake 0900… numbers, no signals, no SMS) and prints
+# Creates N test users (fake 0900… numbers, no signals, no SMS) and prints
 # [{userId, token, grade, asks:[{lessonId, question}], nodeId, questionIds}] as JSON.
 import json
 import os
@@ -18,7 +18,7 @@ out = []
 for i in range(N):
     grade = GRADES[i % len(GRADES)]
     phone = f'{PREFIX}{i:04d}'
-    user, _ = User.objects.get_or_create(phone=phone, defaults={'is_guest': False, 'name': f'تست بار {i}', 'grade_id': grade})
+    user, _ = User.objects.get_or_create(phone=phone, defaults={'name': f'تست بار {i}', 'grade_id': grade})
     qs = list(Question.objects.filter(lesson__node__unit__grade_id=grade).select_related('lesson__node')
               .values_list('id', 'prompt', 'lesson_id', 'lesson__node_id')[:4000])
     picks = rnd.sample(qs, 6)