Reload the browser on template and static changes in dev

Adds django-browser-reload: runserver already restarts on Python changes, but
the browser had to be refreshed by hand for every template or CSS edit. It also
watches static/, so a Tailwind rebuild now refreshes the page on its own.

Mounted only under DEBUG -- it injects a script into every HTML response and
serves an open event stream, neither of which belongs in production; a test
holds that line. Its endpoint is exempt from RequireMFAMiddleware, otherwise a
not-yet-enrolled staff user has the stream redirected away and live reload dies
on the MFA enrolment page, which is exactly a page we are restyling.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

rosterchief/urls.py

@@ -7,6 +7,7 @@ second factors. ``RequireMFAMiddleware`` then blocks any staff user who has not
 enrolled.
 """
 
+from django.conf import settings
 from django.contrib import admin
 from django.urls import include, path
 from django.views.generic import RedirectView
@@ -17,3 +18,6 @@ urlpatterns = [
     path("accounts/", include("allauth.urls")),
     path("controlpanel/", include("controlpanel.urls")),
 ]
+
+if settings.DEBUG:
+    urlpatterns += [path("__reload__/", include("django_browser_reload.urls"))]