Replace inter-service _handlers dicts with declarative sx defquery/defaction

The inter-service data layer (fetch_data/call_action) was the least
structured part of the codebase — Python _handlers dicts with ad-hoc
param extraction scattered across 16 route files. This replaces them
with declarative .sx query/action definitions that make the entire
inter-service protocol self-describing and greppable.

Infrastructure:
- defquery/defaction special forms in the sx evaluator
- Query/action registry with load, lookup, and schema introspection
- Query executor using async_eval with I/O primitives
- Blueprint factories (create_data_blueprint/create_action_blueprint)
  with sx-first dispatch and Python fallback
- /internal/schema endpoint on every service
- parse-datetime and split-ids primitives for type coercion

Service extractions:
- LikesService (toggle, is_liked, liked_slugs, liked_ids)
- PageConfigService (ensure, get_by_container, get_by_id, get_batch, update)
- RelationsService (wraps module-level functions)
- AccountDataService (user_by_email, newsletters)
- CartItemsService, MarketDataService (raw SQLAlchemy lookups)

50 of 54 handlers converted to sx, 4 Python fallbacks remain
(ghost-sync/push-member, clear-cart-for-order, create-order).
Net: -1,383 lines Python, +251 lines modified.

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

shared/services/likes_impl.py

@@ -0,0 +1,103 @@
+"""SQL implementation of the LikesService protocol.
+
+Extracted from likes/bp/data/routes.py and likes/bp/actions/routes.py
+to enable sx defquery/defaction conversion.
+"""
+from __future__ import annotations
+
+from sqlalchemy import select, update, func
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from likes.models.like import Like
+
+
+class SqlLikesService:
+
+    async def is_liked(
+        self, session: AsyncSession, *,
+        user_id: int, target_type: str,
+        target_slug: str | None = None, target_id: int | None = None,
+    ) -> bool:
+        if not user_id or not target_type:
+            return False
+        filters = [
+            Like.user_id == user_id,
+            Like.target_type == target_type,
+            Like.deleted_at.is_(None),
+        ]
+        if target_slug is not None:
+            filters.append(Like.target_slug == target_slug)
+        elif target_id is not None:
+            filters.append(Like.target_id == target_id)
+        else:
+            return False
+        row = await session.scalar(select(Like.id).where(*filters))
+        return row is not None
+
+    async def liked_slugs(
+        self, session: AsyncSession, *,
+        user_id: int, target_type: str,
+    ) -> list[str]:
+        if not user_id or not target_type:
+            return []
+        result = await session.execute(
+            select(Like.target_slug).where(
+                Like.user_id == user_id,
+                Like.target_type == target_type,
+                Like.target_slug.isnot(None),
+                Like.deleted_at.is_(None),
+            )
+        )
+        return list(result.scalars().all())
+
+    async def liked_ids(
+        self, session: AsyncSession, *,
+        user_id: int, target_type: str,
+    ) -> list[int]:
+        if not user_id or not target_type:
+            return []
+        result = await session.execute(
+            select(Like.target_id).where(
+                Like.user_id == user_id,
+                Like.target_type == target_type,
+                Like.target_id.isnot(None),
+                Like.deleted_at.is_(None),
+            )
+        )
+        return list(result.scalars().all())
+
+    async def toggle(
+        self, session: AsyncSession, *,
+        user_id: int, target_type: str,
+        target_slug: str | None = None, target_id: int | None = None,
+    ) -> bool:
+        """Toggle a like. Returns True if now liked, False if unliked."""
+        filters = [
+            Like.user_id == user_id,
+            Like.target_type == target_type,
+            Like.deleted_at.is_(None),
+        ]
+        if target_slug is not None:
+            filters.append(Like.target_slug == target_slug)
+        elif target_id is not None:
+            filters.append(Like.target_id == target_id)
+        else:
+            raise ValueError("target_slug or target_id required")
+
+        existing = await session.scalar(select(Like).where(*filters))
+
+        if existing:
+            await session.execute(
+                update(Like).where(Like.id == existing.id).values(deleted_at=func.now())
+            )
+            return False
+        else:
+            new_like = Like(
+                user_id=user_id,
+                target_type=target_type,
+                target_slug=target_slug,
+                target_id=target_id,
+            )
+            session.add(new_like)
+            await session.flush()
+            return True