feat(fase2): add Flow API routes and Flow Engine main app

API Gateway:
- Add flows router with CRUD endpoints
- Add activate/deactivate endpoints
- Auto-deactivate other flows for welcome/fallback triggers

Flow Engine:
- Add main.py with FastAPI app
- Add /process endpoint for message handling
- Add SQLAlchemy models (mirrors api-gateway)

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

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

@@ -1,4 +1,5 @@
 from app.routers.auth import router as auth_router
 from app.routers.whatsapp import router as whatsapp_router
+from app.routers.flows import router as flows_router
 
-__all__ = ["auth_router", "whatsapp_router"]
+__all__ = ["auth_router", "whatsapp_router", "flows_router"]

services/api-gateway/app/routers/flows.py

@@ -0,0 +1,131 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+from typing import List
+from uuid import UUID
+from app.core.database import get_db
+from app.core.security import get_current_user
+from app.models.user import User, UserRole
+from app.models.flow import Flow, TriggerType
+from app.schemas.flow import FlowCreate, FlowUpdate, FlowResponse, FlowListResponse
+
+router = APIRouter(prefix="/api/flows", tags=["flows"])
+
+
+def require_admin(current_user: User = Depends(get_current_user)):
+    if current_user.role != UserRole.ADMIN:
+        raise HTTPException(status_code=403, detail="Admin required")
+    return current_user
+
+
+@router.get("", response_model=List[FlowListResponse])
+def list_flows(
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    flows = db.query(Flow).order_by(Flow.updated_at.desc()).all()
+    return flows
+
+
+@router.post("", response_model=FlowResponse)
+def create_flow(
+    request: FlowCreate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(require_admin),
+):
+    flow = Flow(
+        name=request.name,
+        description=request.description,
+        trigger_type=request.trigger_type,
+        trigger_value=request.trigger_value,
+        nodes=[],
+        edges=[],
+        variables={},
+    )
+    db.add(flow)
+    db.commit()
+    db.refresh(flow)
+    return flow
+
+
+@router.get("/{flow_id}", response_model=FlowResponse)
+def get_flow(
+    flow_id: UUID,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    flow = db.query(Flow).filter(Flow.id == flow_id).first()
+    if not flow:
+        raise HTTPException(status_code=404, detail="Flow not found")
+    return flow
+
+
+@router.put("/{flow_id}", response_model=FlowResponse)
+def update_flow(
+    flow_id: UUID,
+    request: FlowUpdate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(require_admin),
+):
+    flow = db.query(Flow).filter(Flow.id == flow_id).first()
+    if not flow:
+        raise HTTPException(status_code=404, detail="Flow not found")
+
+    update_data = request.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(flow, field, value)
+
+    flow.version += 1
+    db.commit()
+    db.refresh(flow)
+    return flow
+
+
+@router.delete("/{flow_id}")
+def delete_flow(
+    flow_id: UUID,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(require_admin),
+):
+    flow = db.query(Flow).filter(Flow.id == flow_id).first()
+    if not flow:
+        raise HTTPException(status_code=404, detail="Flow not found")
+
+    db.delete(flow)
+    db.commit()
+    return {"success": True}
+
+
+@router.post("/{flow_id}/activate")
+def activate_flow(
+    flow_id: UUID,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(require_admin),
+):
+    flow = db.query(Flow).filter(Flow.id == flow_id).first()
+    if not flow:
+        raise HTTPException(status_code=404, detail="Flow not found")
+
+    if flow.trigger_type in [TriggerType.WELCOME, TriggerType.FALLBACK]:
+        db.query(Flow).filter(
+            Flow.trigger_type == flow.trigger_type,
+            Flow.id != flow_id
+        ).update({"is_active": False})
+
+    flow.is_active = True
+    db.commit()
+    return {"success": True}
+
+
+@router.post("/{flow_id}/deactivate")
+def deactivate_flow(
+    flow_id: UUID,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(require_admin),
+):
+    flow = db.query(Flow).filter(Flow.id == flow_id).first()
+    if not flow:
+        raise HTTPException(status_code=404, detail="Flow not found")
+
+    flow.is_active = False
+    db.commit()
+    return {"success": True}