fix(api): prevent circular reference in pattern create

src/controllers/pattern.py

@@ -47,11 +47,23 @@ async def get_pattern(request, id):
 async def create_pattern(request):
     """Create a new pattern."""
     try:
-        data = request.json or {}
-        name = data.get("name", "")
-        pattern_id = patterns.create(name, data.get("data", {}))
-        if data:
-            patterns.update(pattern_id, data)
+        payload = request.json or {}
+        name = payload.get("name", "")
+        pattern_data = payload.get("data", {})
+
+        # IMPORTANT:
+        # `patterns.create()` stores `pattern_data` as the underlying dict value.
+        # If we then call `patterns.update(pattern_id, payload)` with the full
+        # request object, it may assign `payload["data"]` back onto that same
+        # dict object, creating a circular reference (json.dumps fails).
+        pattern_id = patterns.create(name, pattern_data)
+
+        # Only merge "extra" metadata fields (anything except name/data).
+        extra = dict(payload)
+        extra.pop("name", None)
+        extra.pop("data", None)
+        if extra:
+            patterns.update(pattern_id, extra)
         return json.dumps(patterns.read(pattern_id)), 201, {'Content-Type': 'application/json'}
     except Exception as e:
         return json.dumps({"error": str(e)}), 400