serve static files via whitenoise under gunicorn

Admin/DRF/Swagger CSS and JS never load under gunicorn since Django's
staticfiles app only auto-serves through `runserver`. WHITENOISE_USE_FINDERS
is tied to DEBUG so no collectstatic step is needed while DEBUG=1.

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

config/settings.py

@@ -104,6 +104,7 @@ INSTALLED_APPS = [
 
 MIDDLEWARE = [
     'django.middleware.security.SecurityMiddleware',
+    'whitenoise.middleware.WhiteNoiseMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.common.CommonMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',
@@ -219,6 +220,18 @@ USE_TZ = True
 # https://docs.djangoproject.com/en/5.2/howto/static-files/
 
 STATIC_URL = 'static/'
+STATIC_ROOT = BASE_DIR / 'staticfiles'
+
+STORAGES = {
+    'default': {
+        'BACKEND': 'django.core.files.storage.FileSystemStorage',
+    },
+    'staticfiles': {
+        'BACKEND': 'whitenoise.storage.CompressedManifestStaticFilesStorage',
+    },
+}
+# با DEBUG=1، از finders مستقیم سرو می‌کنه؛ نیازی به collectstatic نیست.
+WHITENOISE_USE_FINDERS = DEBUG
 
 # -----------------------------------------------------------------------
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