Fix: replace multi-line {# #} comment with single-line form

My previous commit (fb1a8a2) added a multi-line explanatory comment
using Django's {# ... #} syntax, which is single-line only. The comment
therefore rendered as literal text at the top of every page.

This is the second time this session I've made this exact mistake —
lesson for next time: always render a page on the dev server and grep
the response body for '{#' after template changes, even one-liners.
Verified locally this time: leak count = 0.

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

core/templates/base.html

@@ -24,12 +24,8 @@
     <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600&family=Poppins:wght@500;600;700&display=swap" rel="stylesheet">
     <!-- Font Awesome 6 -->
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.5.1/css/all.min.css">
-    <!-- Custom CSS (cache-busted with deployment timestamp) -->
-    {# `deployment_timestamp` is provided by core.context_processors.project_context —
-       it's injected into every template so the browser (and any CDN in front of
-       the app) sees a fresh URL whenever the process restarts. The old template
-       used `request.timestamp` which doesn't exist on Django request objects and
-       always fell back to a fixed '1.0' — meaning CDNs cached the CSS forever. #}
+    <!-- Custom CSS (cache-busted with deployment_timestamp from context processor) -->
+    {# deployment_timestamp comes from core.context_processors.project_context #}
     <link rel="stylesheet" href="{% static 'css/custom.css' %}?v={{ deployment_timestamp|default:'1' }}">
 
     {% block extra_css %}{% endblock %}