feat(fase4): add FlowTemplate model and API

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

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

@@ -0,0 +1,31 @@
+from pydantic import BaseModel
+from typing import Optional, List
+from uuid import UUID
+from datetime import datetime
+
+
+class FlowTemplateCreate(BaseModel):
+    name: str
+    description: Optional[str] = None
+    category: str = "general"
+    nodes: List[dict] = []
+    edges: List[dict] = []
+    variables: dict = {}
+    is_public: bool = True
+
+
+class FlowTemplateResponse(BaseModel):
+    id: UUID
+    name: str
+    description: Optional[str]
+    category: str
+    nodes: List[dict]
+    edges: List[dict]
+    variables: dict
+    preview_image: Optional[str]
+    is_public: bool
+    created_by: UUID
+    created_at: datetime
+
+    class Config:
+        from_attributes = True