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superseded Jinja HTML fragment templates.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>

shared/sexp/templates/relations.sexp

@@ -0,0 +1,15 @@
+(defcomp ~relation-attach (&key create-url label icon)
+  (a :href create-url
+     :hx-get create-url
+     :hx-target "#main-panel"
+     :hx-swap "outerHTML"
+     :hx-push-url "true"
+     :class "flex items-center gap-2 text-sm p-2 rounded hover:bg-stone-100 text-stone-500 hover:text-stone-700 transition-colors"
+    (when icon (i :class icon))
+    (span (or label "Add"))))
+
+(defcomp ~relation-detach (&key detach-url name)
+  (button :hx-delete detach-url
+          :hx-confirm (str "Remove " (or name "this item") "?")
+          :class "text-red-500 hover:text-red-700 text-sm p-1 rounded hover:bg-red-50 transition-colors"
+    (i :class "fa fa-times" :aria-hidden "true")))