feat(fase2): add Flow schemas and Flow Engine core

API Gateway:
- Add Pydantic schemas for Flow API (create, update, response, nodes, edges)

Flow Engine:
- Add FlowContext for variable management and interpolation
- Add FlowEngine for executing chatbot flows
- Support node types: trigger, message, buttons, wait_input, condition, set_variable

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/api-gateway/app/schemas/__init__.py

@@ -6,6 +6,15 @@ from app.schemas.auth import (
     UserResponse,
     CreateUserRequest,
 )
+from app.schemas.flow import (
+    NodeData,
+    FlowNode,
+    FlowEdge,
+    FlowCreate,
+    FlowUpdate,
+    FlowResponse,
+    FlowListResponse,
+)
 
 __all__ = [
     "LoginRequest",
@@ -14,4 +23,11 @@ __all__ = [
     "RefreshRequest",
     "UserResponse",
     "CreateUserRequest",
+    "NodeData",
+    "FlowNode",
+    "FlowEdge",
+    "FlowCreate",
+    "FlowUpdate",
+    "FlowResponse",
+    "FlowListResponse",
 ]