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>

shared/sx/helpers.py

@@ -314,15 +314,15 @@ def sx_call(component_name: str, **kwargs: Any) -> str:
 
 
 def components_for_request() -> str:
-    """Return defcomp source for components the client doesn't have yet.
+    """Return defcomp/defmacro source for definitions the client doesn't have yet.
 
     Reads the ``SX-Components`` header (comma-separated component names
     like ``~card,~nav-item``) and returns only the definitions the client
-    is missing.  If the header is absent, returns all component defs.
+    is missing.  If the header is absent, returns all defs.
     """
     from quart import request
     from .jinja_bridge import client_components_tag, _COMPONENT_ENV
-    from .types import Component
+    from .types import Component, Macro
     from .parser import serialize
 
     loaded_raw = request.headers.get("SX-Components", "")
@@ -338,18 +338,26 @@ def components_for_request() -> str:
     loaded = set(loaded_raw.split(","))
     parts = []
     for key, val in _COMPONENT_ENV.items():
-        if not isinstance(val, Component):
-            continue
-        # Skip components the client already has
-        if f"~{val.name}" in loaded or val.name in loaded:
-            continue
-        # Reconstruct defcomp source
-        param_strs = ["&key"] + list(val.params)
-        if val.has_children:
-            param_strs.extend(["&rest", "children"])
-        params_sx = "(" + " ".join(param_strs) + ")"
-        body_sx = serialize(val.body, pretty=True)
-        parts.append(f"(defcomp ~{val.name} {params_sx} {body_sx})")
+        if isinstance(val, Component):
+            # Skip components the client already has
+            if f"~{val.name}" in loaded or val.name in loaded:
+                continue
+            # Reconstruct defcomp source
+            param_strs = ["&key"] + list(val.params)
+            if val.has_children:
+                param_strs.extend(["&rest", "children"])
+            params_sx = "(" + " ".join(param_strs) + ")"
+            body_sx = serialize(val.body, pretty=True)
+            parts.append(f"(defcomp ~{val.name} {params_sx} {body_sx})")
+        elif isinstance(val, Macro):
+            if val.name in loaded:
+                continue
+            param_strs = list(val.params)
+            if val.rest_param:
+                param_strs.extend(["&rest", val.rest_param])
+            params_sx = "(" + " ".join(param_strs) + ")"
+            body_sx = serialize(val.body, pretty=True)
+            parts.append(f"(defmacro {val.name} {params_sx} {body_sx})")
     return "\n".join(parts)