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>

static/images/rosterchief-white.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="200" height="200">
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+  <rect x="27" y="30" width="46" height="8" rx="4" fill="#0F1A2E"></rect>
+  <rect x="27" y="44" width="34" height="8" rx="4" fill="#0F1A2E"></rect>
+  <path d="M27 80 L50 62 L73 80 L66 85 L50 72 L34 85 Z" fill="#0F1A2E"></path>
+</svg>