feat: add shared child batch creation

schemas/standard_system_operation.schema.json

@@ -15,6 +15,7 @@
         "team_order_batch_create",
         "shared_plan_create",
         "shared_child_order_create",
+        "shared_child_order_batch_create",
         "order_update",
         "passenger_list_import",
         "arrangement_guide",
@@ -235,6 +236,19 @@
         }
       }
     },
+    {
+      "if": {
+        "properties": { "action": { "const": "shared_child_order_batch_create" } },
+        "required": ["action"]
+      },
+      "then": {
+        "properties": {
+          "data": {
+            "required": ["customer", "product", "recurrence", "passenger_counts"]
+          }
+        }
+      }
+    },
     {
       "if": {
         "properties": { "action": { "const": "order_update" } },
@@ -1032,6 +1046,13 @@
           "items": { "$ref": "#/$defs/attachment" }
         },
         "existing_refs": { "$ref": "#/$defs/existingRefs" },
+        "batch_targets": {
+          "type": "array",
+          "minItems": 1,
+          "maxItems": 500,
+          "uniqueItems": true,
+          "items": { "$ref": "#/$defs/sharedPlanBatchTarget" }
+        },
         "updates": {
           "type": "object",
           "description": "Structured update actions. The browser adapter narrows targets again before any write.",
@@ -1137,12 +1158,22 @@
           }
         },
         "stage": { "const": "erp_readonly" },
-        "target": { "const": "unique" },
-        "candidate_count": { "const": 1 },
+        "target": { "type": "string", "enum": ["unique", "batch"] },
+        "candidate_count": { "type": "integer", "minimum": 1, "maximum": 500 },
         "target_kind": { "type": "string", "enum": ["independent_order", "shared_plan", "shared_child_order"] },
         "write_attempted": { "const": false }
       }
     },
+    "sharedPlanBatchTarget": {
+      "type": "object",
+      "additionalProperties": false,
+      "required": ["parent_group_no", "tid", "departure_date"],
+      "properties": {
+        "parent_group_no": { "type": "string", "minLength": 1 },
+        "tid": { "type": "string", "pattern": "^\\d+$" },
+        "departure_date": { "type": "string", "format": "date" }
+      }
+    },
     "namedRef": {
       "type": "object",
       "additionalProperties": false,