feat: trade-pro skeleton theme package (Phase 2)

Fifth built-in theme: English-first international B2B skeleton registered
via manifest discovery, builds real sites end-to-end. pro.html derives
from industrial with lang=en, href-set value-comparison English fallback
nav (header + footer), sf-tp-* button classes and hard-coded #0b3d91
theme-color until the map entry lands. pages/ ships all 14 kinds; macro
library is an English passthrough copy pending the Phase 3 cms port.

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

themes/trade-pro/pages/listing.html

@@ -0,0 +1,2 @@
+<section class="pro-inner-hero pro-listing-hero"><div class="pro-wrap"><span class="pro-eyebrow">DISCOVER / {{'CATEGORY' if kind=='category' else 'COLLECTION'}}</span><h1>{{page.title}}</h1><p>{{page.summary or 'Browse all published content in this section.'}}</p><div class="pro-breadcrumb"><a href="/">Home</a><span>／</span><strong>{{page.title}}</strong></div></div></section>
+<section class="pro-section pro-list-section"><div class="pro-wrap">{{ filters() }}<div class="pro-filter-scope">{{grid(listing,'catalog')}}</div>{% if pagination and pagination.pages>1 %}<nav class="pro-pages-nav" aria-label="Catalogue pagination">{% if pagination.previous %}<a href="{{pagination.previous}}" rel="prev">← Previous</a>{% endif %}<span>Page {{pagination.page}} of {{pagination.pages}}</span>{% if pagination.next %}<a href="{{pagination.next}}" rel="next">Next →</a>{% endif %}</nav>{% endif %}</div></section>