fix(dev): simplify Debug Toolbar wiring (review followups)

Three followups on 7075269:

- config/urls.py: drop dead try/except ImportError fallback.
  The settings.py gate already guarantees debug_toolbar is
  importable before we reach this line, so the except branch
  was unreachable and the re-import of include/path was
  redundant (both imported at top of file).

- config/settings.py: SHOW_TOOLBAR_CALLBACK now returns True
  unconditionally. The triple gate passed at settings-load time,
  so re-checking DEBUG and _IS_DEV inside the lambda was
  redundant. Comment corrected — the callback has nothing to
  do with "stale cached pages".

- requirements.txt: inline comment noting django-debug-toolbar
  is dev-only and gated.

No behavioural change. Tests: 68/68.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

config/settings.py

@@ -334,7 +334,9 @@ if DEBUG and _IS_DEV and not _IS_RUNNING_TESTS:
             # Don't auto-collapse the SQL panel — the SQL count is the
             # main thing we check on every page.
             'SHOW_COLLAPSED': False,
-            # Explicit check so the toolbar ONLY renders when the hosting
-            # flags are still set (guards against stale cached pages).
-            'SHOW_TOOLBAR_CALLBACK': lambda request: DEBUG and _IS_DEV,
+            # This callback is invoked per-request by the toolbar's middleware.
+            # Since we only REACH this config block when the triple gate
+            # (DEBUG + _IS_DEV + not running tests) already passed at settings
+            # load time, there's nothing to re-check here — just return True.
+            'SHOW_TOOLBAR_CALLBACK': lambda request: True,
         }

config/urls.py

@@ -15,11 +15,10 @@ if settings.DEBUG:
 
 # === DEV-ONLY: Django Debug Toolbar URL include ===
 # Matches the conditional load in settings.py. No-op in prod.
+# The settings.py gate already guarantees debug_toolbar is importable
+# by the time we get here, so no try/except is needed. If we ever
+# downgrade to a toolbar version older than v4.0 (which introduced
+# debug_toolbar_urls), swap this for `path('__debug__/', include(debug_toolbar.urls))`.
 if 'debug_toolbar' in settings.INSTALLED_APPS:
-    try:
-        from debug_toolbar.toolbar import debug_toolbar_urls
-        urlpatterns += debug_toolbar_urls()
-    except ImportError:
-        import debug_toolbar
-        from django.urls import include, path
-        urlpatterns += [path('__debug__/', include(debug_toolbar.urls))]
+    from debug_toolbar.toolbar import debug_toolbar_urls
+    urlpatterns += debug_toolbar_urls()

requirements.txt

@@ -3,4 +3,4 @@ mysqlclient==2.2.7
 python-dotenv==1.1.1
 pillow==12.1.1
 weasyprint==68.1
-django-debug-toolbar==6.0.0
+django-debug-toolbar==6.0.0  # dev-only — gated in config/settings.py, never active in prod