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/notfound.html

@@ -1 +1 @@
-<section class="pro-404 pro-wrap"><span>ERROR / 404</span><h1>404</h1><p>The page you are looking for does not exist or has been moved.</p><a class="sf-tp-btn" href="/">Back to home ↗</a></section>
+<section class="pro-404 pro-wrap"><span>ERROR / 404</span><h1>404</h1><p>The page you are looking for does not exist or has been moved.</p><a class="sf-tp-btn" href="/">Back to home {{ icon('arrow-right') }}</a></section>