Add macros, declarative handlers (defhandler), and convert all fragment routes to sx

Phase 1 — Macros: defmacro + quasiquote syntax (`, ,, ,@) in parser,
evaluator, HTML renderer, and JS mirror. Macro type, expansion, and
round-trip serialization.

Phase 2 — Expanded primitives: app-url, url-for, asset-url, config,
format-date, parse-int (pure); service, request-arg, request-path,
nav-tree, get-children (I/O); jinja-global, relations-from (pure).
Updated _io_service to accept (service "registry-name" "method" :kwargs)
with auto kebab→snake conversion. DTO-to-dict now expands datetime fields
into year/month/day convenience keys. Tuple returns converted to lists.

Phase 3 — Declarative handlers: HandlerDef type, defhandler special form,
handler registry (service → name → HandlerDef), async evaluator+renderer
(async_eval.py) that awaits I/O primitives inline within control flow.
Handler loading from .sx files, execute_handler, blueprint factory.

Phase 4 — Convert all fragment routes: 13 Python fragment handlers across
8 services replaced with declarative .sx handler files. All routes.py
simplified to uniform sx dispatch pattern. Two Jinja HTML handlers
(events/container-cards, events/account-page) kept as Python.

New files: shared/sx/async_eval.py, shared/sx/handlers.py,
shared/sx/tests/test_handlers.py, plus 13 handler .sx files under
{service}/sx/handlers/. MarketService.product_by_slug() added.

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

relations/sx/handlers/container-nav.sx

@@ -0,0 +1,47 @@
+;; Relations container-nav fragment handler
+;;
+;; Generic navigation fragment driven by the relation registry.
+;; Renders nav items for all related entities of a container.
+
+(defhandler container-nav (&key container_type container_id post_slug nav_class exclude)
+  (let ((ct          (or container_type "page"))
+        (cid         (parse-int (or container_id "0")))
+        (slug        (or post_slug ""))
+        (ncls        (or nav_class ""))
+        (excl-raw    (or exclude ""))
+        (excl-set    (filter (fn (e) (not (empty? e)))
+                       (map trim (split excl-raw ","))))
+
+        ;; URL builders per child type
+        (url-builders (dict :calendar "events" :market "market"))
+
+        ;; Filter relation defs: visible + not excluded
+        (nav-defs    (filter (fn (d)
+                       (and (!= (get d "nav") "hidden")
+                            (not (contains? excl-set (get d "name")))))
+                       (relations-from ct))))
+
+    (when (not (empty? nav-defs))
+      (let ((parts (map (fn (defn)
+              (let ((children (get-children
+                                :parent-type ct
+                                :parent-id cid
+                                :child-type (get defn "to_type")
+                                :relation-type (get defn "name"))))
+                (<> (map (fn (child)
+                  (let ((child-slug (or (get (or (get child "metadata_") (dict)) "slug") "")))
+                    (when (not (empty? child-slug))
+                      (let ((path (if (not (empty? slug))
+                                    (str "/" slug "/" child-slug "/")
+                                    (str "/" child-slug "/")))
+                            (svc-name (get url-builders (get defn "to_type")))
+                            (href (if svc-name
+                                    (app-url svc-name path)
+                                    path)))
+                        (~relation-nav
+                          :href href
+                          :name (or (get child "label") "")
+                          :icon (or (get defn "nav_icon") "")
+                          :nav-class ncls
+                          :relation-type (get defn "name")))))) children)))) nav-defs)))
+        (<> parts)))))

relations/sx/sx_components.py

@@ -0,0 +1,14 @@
+"""
+Relations service s-expression components.
+
+Loads relation-specific .sx components and handlers.
+"""
+from __future__ import annotations
+
+import os
+
+from shared.sx.jinja_bridge import load_service_components
+
+# Load relations-specific .sx components + handlers at import time
+load_service_components(os.path.dirname(os.path.dirname(__file__)),
+                        service_name="relations")