give every developer a way into the API that does not depend on one person

With DEBUG=0 and Kavenegar unconfigured, POST /api/auth/otp/request returns a
hard 503, so the only way to sign in was for someone with admin access to hand-
create an OTPCode row. That made every frontend developer's login depend on one
person being available.

TEST_LOGIN_PHONES is the pattern real apps use for exactly this (Firebase Auth's
fictional numbers, Apple's App Store demo account): a short allowlist of
phone:code pairs that skip SMS delivery entirely. Unlike DEV_MASTER_OTP it is
not "any phone with one code" and it is not tied to DEBUG -- each number carries
its own code, and everything else takes the normal OTP path untouched.

The code never appears in an API response, so knowing the number is not enough
to log in, and the existing per-phone login attempt limit still applies, so the
code cannot be brute-forced. Malformed configuration raises ImproperlyConfigured
at startup rather than being skipped silently, and /api/health reports how many
test numbers are open (count only) so they cannot be forgotten on a server that
has real users.

The code is capped at six digits because LoginRequestSerializer caps otp at
max_length=6; a longer code would have been rejected before reaching the check
and looked like the feature was broken.

The guest path the frontend uses today is untouched, and leaving the variable
empty reproduces the previous behaviour exactly.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

config/health.py

@@ -132,6 +132,14 @@ def _warnings() -> list[str]:
         )
     if getattr(settings, 'DEV_MASTER_OTP', None) is not None:
         out.append('کدِ یک‌سانِ ورود (DEV_MASTER_OTP) فعال است — هر کسی می‌تواند به‌جای هر کاربری وارد شود.')
+    test_phones = getattr(settings, 'TEST_LOGIN_PHONES', {})
+    if test_phones:
+        # نه خودِ شماره و نه کد برنمی‌گردد؛ فقط تعداد، تا کسی که تنظیماتِ سرور
+        # را ندیده هم بداند چند حسابِ تست با کدِ ثابت باز است و بتواند ببنددشان.
+        out.append(
+            f'{len(test_phones)} شماره‌ی تستِ ورود با کدِ ثابت تعریف شده (TEST_LOGIN_PHONES). '
+            'برای توسعه لازم است؛ پیش از تحویلِ نهایی به کاربرانِ واقعی حذفشان کنید.'
+        )
     backend = settings.CACHES['default']['BACKEND']
     if not settings.DEBUG and 'LocMem' in backend:
         out.append('کش محلیِ هر پروسه است؛ محدودیتِ نرخ بینِ workerها مشترک نیست.')