feat: add MarketPlace model, migration, and market_url_for helper

Introduces per-page markets (Phase 2):
- MarketPlace model with soft-delete and unique slug index
- NavTop gains market_id FK to scope nav hierarchy per market
- Migration with backfill creates default 'suma-market' for existing market page
- market_url_for() cross-app URL helper

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

models/__init__.py

@@ -14,6 +14,7 @@ from .ghost_membership_entities import (
 
 from .calendars import Calendar, CalendarEntry, Ticket
 from .page_config import PageConfig
+from .market_place import MarketPlace
 
 
 

models/ghost_content.py

@@ -172,6 +172,14 @@ class Post(Base):
         passive_deletes=True,
     )
 
+    markets: Mapped[List["MarketPlace"]] = relationship(
+        "MarketPlace",
+        back_populates="post",
+        cascade="all, delete-orphan",
+        passive_deletes=True,
+        order_by="MarketPlace.name",
+    )
+
 class Author(Base):
     __tablename__ = "authors"
 

models/market.py

@@ -186,11 +186,18 @@ class NavTop(Base):
     id: Mapped[int] = mapped_column(primary_key=True)
     label: Mapped[str] = mapped_column(String(255), nullable=False)
     slug: Mapped[str] = mapped_column(String(255), nullable=False, index=True)
+    market_id: Mapped[Optional[int]] = mapped_column(
+        Integer,
+        ForeignKey("market_places.id", ondelete="SET NULL"),
+        nullable=True,
+        index=True,
+    )
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())
     updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())
     deleted_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True))
-    
+
     listings: Mapped[List["Listing"]] = relationship(back_populates="top", cascade="all, delete-orphan")
+    market = relationship("MarketPlace", back_populates="nav_tops")
 
     __table_args__ = (UniqueConstraint("label", "slug", name="uq_nav_tops_label_slug"),)
 

models/market_place.py

@@ -0,0 +1,54 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import Optional, List
+
+from sqlalchemy import (
+    Integer, String, Text, DateTime, ForeignKey, Index, func, text,
+)
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from db.base import Base
+
+
+def utcnow() -> datetime:
+    return datetime.now(timezone.utc)
+
+
+class MarketPlace(Base):
+    __tablename__ = "market_places"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    post_id: Mapped[int] = mapped_column(
+        Integer,
+        ForeignKey("posts.id", ondelete="CASCADE"),
+        nullable=False,
+    )
+    name: Mapped[str] = mapped_column(String(255), nullable=False)
+    slug: Mapped[str] = mapped_column(String(255), nullable=False)
+    description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now(),
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now(),
+    )
+    deleted_at: Mapped[Optional[datetime]] = mapped_column(
+        DateTime(timezone=True), nullable=True,
+    )
+
+    post = relationship("Post", back_populates="markets")
+    nav_tops: Mapped[List["NavTop"]] = relationship(
+        "NavTop", back_populates="market",
+    )
+
+    __table_args__ = (
+        Index("ix_market_places_post_id", "post_id"),
+        Index(
+            "ux_market_places_slug_active",
+            func.lower(slug),
+            unique=True,
+            postgresql_where=text("deleted_at IS NULL"),
+        ),
+    )