add fixture-invoicing example, sample-room wrap, kind cluster support

- examples/fixture-invoicing/: FastAPI + Vue + Postgres demo (4-entity invoice fixture)
- cfg/sample/: wraps the fixture (managed.repos points at examples/)
- ctrl/kind-{up,down,status}.sh + per-room k8s render in soleprint/ctrl/k8s/
- build.py: relative repo paths, resilient rmtree, optional k8s render hook
- cfg/.gitignore: stop ignoring sample/ and standalone/ template rooms

Manifests render cleanly but kind cluster has not been run end-to-end yet.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

examples/fixture-invoicing/backend/api/customers.py

@@ -0,0 +1,53 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from db import get_session
+from models import Customer
+from schemas import CustomerIn, CustomerOut
+
+router = APIRouter()
+
+
+@router.get("", response_model=list[CustomerOut])
+def list_customers(session: Session = Depends(get_session)):
+    return session.query(Customer).order_by(Customer.id).all()
+
+
+@router.post("", response_model=CustomerOut, status_code=201)
+def create_customer(payload: CustomerIn, session: Session = Depends(get_session)):
+    customer = Customer(**payload.model_dump())
+    session.add(customer)
+    session.commit()
+    session.refresh(customer)
+    return customer
+
+
+@router.get("/{customer_id}", response_model=CustomerOut)
+def get_customer(customer_id: int, session: Session = Depends(get_session)):
+    customer = session.get(Customer, customer_id)
+    if not customer:
+        raise HTTPException(404, "customer not found")
+    return customer
+
+
+@router.put("/{customer_id}", response_model=CustomerOut)
+def update_customer(
+    customer_id: int, payload: CustomerIn, session: Session = Depends(get_session)
+):
+    customer = session.get(Customer, customer_id)
+    if not customer:
+        raise HTTPException(404, "customer not found")
+    for k, v in payload.model_dump().items():
+        setattr(customer, k, v)
+    session.commit()
+    session.refresh(customer)
+    return customer
+
+
+@router.delete("/{customer_id}", status_code=204)
+def delete_customer(customer_id: int, session: Session = Depends(get_session)):
+    customer = session.get(Customer, customer_id)
+    if not customer:
+        raise HTTPException(404, "customer not found")
+    session.delete(customer)
+    session.commit()