feat: add markets and payments management pages

- New markets blueprint at /<slug>/markets/ with create/delete
- New payments blueprint at /<slug>/payments/ with SumUp config
- Register both in events app with context processor for markets
- Remove PageConfig feature flag check from calendar creation
  (feature toggles replaced by direct management pages)

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

app.py

@@ -9,7 +9,7 @@ from sqlalchemy import select
 
 from shared.factory import create_base_app
 
-from suma_browser.app.bp import register_calendars
+from suma_browser.app.bp import register_calendars, register_markets, register_payments
 
 
 async def events_context() -> dict:
@@ -43,6 +43,7 @@ async def events_context() -> dict:
 def create_app() -> "Quart":
     from models.ghost_content import Post
     from models.calendars import Calendar
+    from models.market_place import MarketPlace
 
     app = create_base_app("events", context_fn=events_context)
 
@@ -59,6 +60,18 @@ def create_app() -> "Quart":
         url_prefix="/<slug>/calendars",
     )
 
+    # Markets nested under post slug: /<slug>/markets/...
+    app.register_blueprint(
+        register_markets(),
+        url_prefix="/<slug>/markets",
+    )
+
+    # Payments nested under post slug: /<slug>/payments/...
+    app.register_blueprint(
+        register_payments(),
+        url_prefix="/<slug>/payments",
+    )
+
     # --- Auto-inject slug into url_for() calls ---
     @app.url_value_preprocessor
     def pull_slug(endpoint, values):
@@ -109,9 +122,17 @@ def create_app() -> "Quart":
                 .order_by(Calendar.name.asc())
             )
         ).scalars().all()
+        markets = (
+            await g.s.execute(
+                select(MarketPlace)
+                .where(MarketPlace.post_id == post_id, MarketPlace.deleted_at.is_(None))
+                .order_by(MarketPlace.name.asc())
+            )
+        ).scalars().all()
         return {
             **post_data,
             "calendars": calendars,
+            "markets": markets,
         }
 
     # Tickets blueprint — user-facing ticket views and QR codes