Add error handling to action endpoint dispatchers

Unhandled exceptions in action handlers were returned as opaque
400/500 by Quart's default error handler. Now we catch, log the
full traceback, and return a JSON error body with 500 status so
the caller gets useful diagnostics.

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

cart/bp/actions/routes.py

@@ -26,8 +26,13 @@ def register() -> Blueprint:
         handler = _handlers.get(action_name)
         if handler is None:
             return jsonify({"error": "unknown action"}), 404
-        result = await handler()
-        return jsonify(result)
+        try:
+            result = await handler()
+            return jsonify(result)
+        except Exception as exc:
+            import logging
+            logging.getLogger(__name__).exception("Action %s failed", action_name)
+            return jsonify({"error": str(exc)}), 500
 
     # --- adopt-cart-for-user ---
     async def _adopt_cart():

events/bp/actions/routes.py

@@ -26,8 +26,13 @@ def register() -> Blueprint:
         handler = _handlers.get(action_name)
         if handler is None:
             return jsonify({"error": "unknown action"}), 404
-        result = await handler()
-        return jsonify(result)
+        try:
+            result = await handler()
+            return jsonify(result)
+        except Exception as exc:
+            import logging
+            logging.getLogger(__name__).exception("Action %s failed", action_name)
+            return jsonify({"error": str(exc)}), 500
 
     # --- adjust-ticket-quantity ---
     async def _adjust_ticket_quantity():

market/bp/actions/routes.py

@@ -26,8 +26,13 @@ def register() -> Blueprint:
         handler = _handlers.get(action_name)
         if handler is None:
             return jsonify({"error": "unknown action"}), 404
-        result = await handler()
-        return jsonify(result)
+        try:
+            result = await handler()
+            return jsonify(result)
+        except Exception as exc:
+            import logging
+            logging.getLogger(__name__).exception("Action %s failed", action_name)
+            return jsonify({"error": str(exc)}), 500
 
     # --- create-marketplace ---
     async def _create_marketplace():