Externalize sexp component templates and delete redundant HTML fragments

Move 24 defcomp definitions from Python string constants in components.py
to 7 grouped .sexp files under shared/sexp/templates/. Add load_sexp_dir()
to jinja_bridge.py for file-based loading. Migrate events and market
link-card fragment handlers from render_template to sexp. Delete 9
superseded Jinja HTML fragment templates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cart/templates/fragments/cart_mini.html

@@ -1,27 +0,0 @@
-<div id="cart-mini" {% if oob %}hx-swap-oob="true"{% endif %}>
-  {% if cart_count == 0 %}
-  <div class="h-12 w-12 rounded-full overflow-hidden border border-stone-300 flex-shrink-0">
-    <a
-      href="{{ blog_url('/') }}"
-      class="h-full w-full font-bold text-5xl flex-shrink-0 flex flex-row items-center gap-1"
-    >
-      <img
-        src="{{ blog_url('/static/img/logo.jpg') }}"
-        class="h-full w-full rounded-full object-cover border border-stone-300 flex-shrink-0"
-      >
-    </a>
-  </div>
-  {% else %}
-    <a
-      href="{{ cart_url('/') }}"
-      class="relative inline-flex items-center justify-center text-stone-700 hover:text-emerald-700"
-    >
-      <i class="fa fa-shopping-cart text-5xl" aria-hidden="true"></i>
-      <span
-        class="absolute top-1/2 left-1/2 -translate-x-1/2 -translate-y-1/2 inline-flex items-center justify-center rounded-full bg-emerald-600 text-white text-sm w-5 h-5"
-      >
-        {{ cart_count }}
-      </span>
-    </a>
-  {% endif %}
-</div>