feat: SVG icon macro library replaces bare text arrows in trade-pro

Task 9 (new design, not a cms port): _professional_components.html gains
an icon(name, size, cls) macro — 10 inline line-style glyphs (arrow-right,
arrow-left, chevron-down, check, phone, mail, location, download, search,
quote), 24x24 viewBox, stroke=currentColor, stroke-width 1.5, round
caps/joins, decorative aria-hidden + focusable=false, default size
var(--sf-tp-icon-size-md, 20px), unknown names fall back to arrow-right.
Every glyph is a single <path> so the d attribute needs no |safe.

All bare text arrows (->, <-, ↗, ▾, ⌕) in the macro library, pro.html,
site.html and pages/* are replaced with macro calls (site.html keeps a
self-contained copy of the arrow glyph because its rendering envs cannot
import the macro library); the filters macro search box gains an inline
search icon; footer links gain small arrows. theme.css adds .sf-tp-icon
alignment, in-button icon spacing, and search-box icon positioning.

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

themes/trade-pro/pages/category.html

@@ -1,2 +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>
+<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">{{ icon('arrow-left') }} Previous</a>{% endif %}<span>Page {{pagination.page}} of {{pagination.pages}}</span>{% if pagination.next %}<a href="{{pagination.next}}" rel="next">Next {{ icon('arrow-right') }}</a>{% endif %}</nav>{% endif %}</div></section>