Drop a redundant inline margin from the Storage fallback note

The container-disk-usage note carried style="margin-bottom:0", which
326ab6c had already covered with `.meter-legend + .empty`. The <p> is
that rule's adjacent sibling in the rendered output (the Jinja {% if %}
around it emits no element), so the inline copy was doing nothing and
violated CLAUDE.md's no-static-inline-style rule for no benefit.

Verified the computed margin-bottom is still 0 with the attribute gone.
The eight remaining inline styles are the kinds the rule allows —
Jinja-computed meter widths and threshold colours, and display:none on
elements dashboard.js reveals.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

templates/dashboard.html

@@ -262,7 +262,7 @@
             </div>
             <div class="meter-legend"><span>{{ unraid.array_used }} used</span></div>
             {% if unraid.source == "local" %}
-            <p class="empty" style="margin-bottom:0;">Container disk usage ({{ unraid.mount }}). Set <code>UNRAID_API_KEY</code> for full array stats.</p>
+            <p class="empty">Container disk usage ({{ unraid.mount }}). Set <code>UNRAID_API_KEY</code> for full array stats.</p>
             {% endif %}
             {% endif %}