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>

bp/payments/routes.py

@@ -0,0 +1,81 @@
+from __future__ import annotations
+
+from quart import (
+    render_template, make_response, Blueprint, g, request
+)
+from sqlalchemy import select
+
+from models.page_config import PageConfig
+
+from suma_browser.app.authz import require_admin
+from suma_browser.app.utils.htmx import is_htmx_request
+
+
+def register():
+    bp = Blueprint("payments", __name__, url_prefix='/payments')
+
+    @bp.context_processor
+    async def inject_root():
+        return {}
+
+    async def _load_payment_ctx():
+        """Load PageConfig SumUp data for the current page."""
+        post = (getattr(g, "post_data", None) or {}).get("post", {})
+        post_id = post.get("id")
+        if not post_id:
+            return {}
+
+        pc = (await g.s.execute(
+            select(PageConfig).where(PageConfig.post_id == post_id)
+        )).scalar_one_or_none()
+
+        return {
+            "sumup_configured": bool(pc and pc.sumup_api_key),
+            "sumup_merchant_code": (pc.sumup_merchant_code or "") if pc else "",
+            "sumup_checkout_prefix": (pc.sumup_checkout_prefix or "") if pc else "",
+        }
+
+    @bp.get("/")
+    @require_admin
+    async def home(**kwargs):
+        ctx = await _load_payment_ctx()
+        if not is_htmx_request():
+            html = await render_template("_types/payments/index.html", **ctx)
+        else:
+            html = await render_template("_types/payments/_oob_elements.html", **ctx)
+        return await make_response(html)
+
+    @bp.put("/")
+    @require_admin
+    async def update_sumup(**kwargs):
+        """Update SumUp credentials for this page."""
+        post = (getattr(g, "post_data", None) or {}).get("post", {})
+        post_id = post.get("id")
+        if not post_id:
+            return await make_response("Post not found", 404)
+
+        pc = (await g.s.execute(
+            select(PageConfig).where(PageConfig.post_id == post_id)
+        )).scalar_one_or_none()
+        if pc is None:
+            pc = PageConfig(post_id=post_id, features={})
+            g.s.add(pc)
+            await g.s.flush()
+
+        form = await request.form
+        merchant_code = (form.get("merchant_code") or "").strip()
+        api_key = (form.get("api_key") or "").strip()
+        checkout_prefix = (form.get("checkout_prefix") or "").strip()
+
+        pc.sumup_merchant_code = merchant_code or None
+        pc.sumup_checkout_prefix = checkout_prefix or None
+        if api_key:
+            pc.sumup_api_key = api_key
+
+        await g.s.flush()
+
+        ctx = await _load_payment_ctx()
+        html = await render_template("_types/payments/_main_panel.html", **ctx)
+        return await make_response(html)
+
+    return bp