fix: sparkline sizing — use div wrapper instead of span in flex context

The sparkline SVG containers were using <span> elements as flex items.
While a span's outer display is blockified in flex context, its inner
display remains inline, causing SVG width:100% to resolve against the
inline content width (~22px) instead of the flex-allocated width (~670px).
Switching to <div> provides block inner display, allowing the SVG to
fill the available space correctly.

Confab-Link: http://localhost:8080/sessions/0ec83454-d346-4329-8aaf-6b12139bf596

notes.njk

@@ -14,7 +14,7 @@ permalink: "notes/{% if pagination.pageNumber > 0 %}page/{{ pagination.pageNumbe
     <h1 class="text-2xl sm:text-3xl font-bold text-surface-900 dark:text-surface-100">Notes</h1>
     {% set sparklineSvg = collections.notes | postingFrequency %}
     {% if sparklineSvg %}
-    <span class="flex-1 min-w-0 text-amber-600 dark:text-amber-400">{{ sparklineSvg | safe }}</span>
+    <div class="flex-1 min-w-0 text-amber-600 dark:text-amber-400">{{ sparklineSvg | safe }}</div>
     {% endif %}
   </div>
   <p class="text-surface-600 dark:text-surface-400 mb-6 sm:mb-8">