Serve /health and keep 404 scanner noise out of the log file

Something on the network polls /health (and /v1/models) every 30 seconds;
the former now answers 200 with a database check instead of a 404, and
django.request is limited to ERROR in the logging config so scanner 404s
stop filling backend/logs/j621.log. Real server errors still log, and the
dev server keeps printing every request to its console.

backend/config/settings.py

@@ -238,6 +238,16 @@ LOGGING = {
         },
     },
     "handlers": _log_handlers,
+    "loggers": {
+        # Scanners on the network probe things like /health and /v1/models;
+        # their 404s are noise in the log file. Real server errors (5xx) still
+        # log, and the dev server keeps printing every request to the console.
+        "django.request": {
+            "handlers": _root_handlers,
+            "level": "ERROR",
+            "propagate": False,
+        },
+    },
     "root": {
         "handlers": _root_handlers,
         "level": "INFO",

backend/config/urls.py

@@ -3,6 +3,8 @@ from django.conf.urls.static import static
 from django.contrib import admin
 from django.urls import include, path
 
+from apps.core.views import HealthView
+
 urlpatterns = [
     path("admin/", admin.site.urls),
     path("api/auth/", include("apps.accounts.urls")),
@@ -10,6 +12,9 @@ urlpatterns = [
     path("api/", include("apps.core.urls")),
     path("api/", include("apps.library.urls")),
     path("api/", include("apps.follows.urls")),
+    # Liveness probe for uptime monitors (no /api prefix, no auth).
+    path("health", HealthView.as_view(), name="health"),
+    path("health/", HealthView.as_view()),
 ]
 
 if settings.DEBUG: