feat: per-page SumUp admin UI and update_sumup route (Phase 3)

- Replace SumUp placeholder with real form for merchant code, API key, prefix
- Add PUT /admin/sumup/ route to save per-page SumUp credentials
- Pass sumup_configured/merchant_code/checkout_prefix to template context
- SumUp form only shown when calendar or market feature is enabled

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

bp/post/admin/routes.py

@@ -28,14 +28,25 @@ def register():
     # Load features for page admin
     post = (g.post_data or {}).get("post", {})
     features = {}
+    sumup_configured = False
+    sumup_merchant_code = ""
+    sumup_checkout_prefix = ""
     if post.get("is_page"):
         pc = (await g.s.execute(
             sa_select(PageConfig).where(PageConfig.post_id == post["id"])
         )).scalar_one_or_none()
         if pc:
             features = pc.features or {}
+            sumup_configured = bool(pc.sumup_api_key)
+            sumup_merchant_code = pc.sumup_merchant_code or ""
+            sumup_checkout_prefix = pc.sumup_checkout_prefix or ""
 
-    ctx = {"features": features}
+    ctx = {
+        "features": features,
+        "sumup_configured": sumup_configured,
+        "sumup_merchant_code": sumup_merchant_code,
+        "sumup_checkout_prefix": sumup_checkout_prefix,
+    }
 
     # Determine which template to use based on request type
     if not is_htmx_request():
@@ -104,6 +115,53 @@ def register():
         "_types/post/admin/_features_panel.html",
         features=features,
         post=post,
+        sumup_configured=bool(pc.sumup_api_key),
+        sumup_merchant_code=pc.sumup_merchant_code or "",
+        sumup_checkout_prefix=pc.sumup_checkout_prefix or "",
+    )
+    return await make_response(html)
+
+  @bp.put("/admin/sumup/")
+  @require_admin
+  async def update_sumup(slug: str):
+    """Update PageConfig SumUp credentials for a page."""
+    from models.page_config import PageConfig
+    from sqlalchemy import select as sa_select
+    from quart import jsonify
+
+    post = g.post_data.get("post")
+    if not post or not post.get("is_page"):
+        return jsonify({"error": "This is not a page."}), 400
+
+    post_id = post["id"]
+
+    pc = (await g.s.execute(
+        sa_select(PageConfig).where(PageConfig.post_id == post_id)
+    )).scalar_one_or_none()
+    if pc is None:
+        return jsonify({"error": "PageConfig not found for this page."}), 404
+
+    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
+    # Only update API key if non-empty (allows updating other fields without re-entering key)
+    if api_key:
+        pc.sumup_api_key = api_key
+
+    await g.s.flush()
+
+    features = pc.features or {}
+    html = await render_template(
+        "_types/post/admin/_features_panel.html",
+        features=features,
+        post=post,
+        sumup_configured=bool(pc.sumup_api_key),
+        sumup_merchant_code=pc.sumup_merchant_code or "",
+        sumup_checkout_prefix=pc.sumup_checkout_prefix or "",
     )
     return await make_response(html)