Fix cross-DB queries: move page_configs to cart, fix OAuth code_hash lookup

page_configs table lives in db_cart but blog was querying it directly,
causing UndefinedTableError. Move all PageConfig read/write endpoints to
cart service and have blog proxy via fetch_data/call_action.

Also fix OAuth callback to use code_hash lookup (codes are now stored
hashed) and pass grant_token in redirect URL to prevent auth loops.

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

blog/bp/blog/ghost_db.py

@@ -6,7 +6,6 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import selectinload, joinedload
 
 from models.ghost_content import Post, Author, Tag, PostTag
-from shared.models.page_config import PageConfig
 from models.tag_group import TagGroup, TagGroupTag
 
 
@@ -280,7 +279,6 @@ class DBClient:
                 joinedload(Post.primary_tag),
                 selectinload(Post.authors),
                 selectinload(Post.tags),
-                joinedload(Post.page_config),
             )
             .limit(limit)
             .offset(offset_val)
@@ -288,10 +286,24 @@ class DBClient:
 
         rows: List[Post] = list((await self.sess.execute(q)).scalars())
 
+        # Load PageConfigs from cart service (page_configs lives in db_cart)
+        post_ids = [p.id for p in rows]
+        pc_map: Dict[int, dict] = {}
+        if post_ids:
+            from shared.infrastructure.data_client import fetch_data
+            try:
+                raw_pcs = await fetch_data("cart", "page-configs-batch",
+                    params={"container_type": "page", "ids": ",".join(str(i) for i in post_ids)})
+                if isinstance(raw_pcs, list):
+                    for pc in raw_pcs:
+                        pc_map[pc["container_id"]] = pc
+            except Exception:
+                pass  # graceful degradation — pages render without features
+
         def _page_to_public(p: Post) -> Dict[str, Any]:
             d = _post_to_public(p)
-            pc = p.page_config
-            d["features"] = pc.features if pc else {}
+            pc = pc_map.get(p.id)
+            d["features"] = pc["features"] if pc else {}
             return d
 
         pages_list = [_page_to_public(p) for p in rows]