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>

cfg/sample/link/Dockerfile

@@ -0,0 +1,15 @@
+FROM python:3.12-slim
+
+WORKDIR /app
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libpq-dev gcc \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+EXPOSE 8000
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000", "--reload"]

cfg/sample/link/adapters/sqlalchemy_bridge.py

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+"""SQLAlchemy bridge — read tables via reflection.
+
+Works against the fixture's postgres. Reflection means the link does not
+need to import the app's model code — it discovers tables at runtime.
+"""
+
+import os
+
+from fastapi import APIRouter, HTTPException
+from sqlalchemy import MetaData, create_engine, inspect, select
+
+router = APIRouter()
+
+
+def _db_url() -> str:
+    host = os.getenv("DB_HOST", "db")
+    port = os.getenv("DB_PORT", "5432")
+    name = os.getenv("DB_NAME", "fixture")
+    user = os.getenv("DB_USER", "postgres")
+    password = os.getenv("DB_PASSWORD", "localdev123")
+    return f"postgresql+psycopg2://{user}:{password}@{host}:{port}/{name}"
+
+
+engine = create_engine(_db_url(), future=True)
+metadata = MetaData()
+
+
+@router.get("/tables")
+def list_tables():
+    insp = inspect(engine)
+    return {"tables": insp.get_table_names()}
+
+
+@router.get("/tables/{name}")
+def table_rows(name: str, limit: int = 50):
+    insp = inspect(engine)
+    if name not in insp.get_table_names():
+        raise HTTPException(404, f"table '{name}' not found")
+    metadata.reflect(bind=engine, only=[name])
+    table = metadata.tables[name]
+    with engine.connect() as conn:
+        rows = conn.execute(select(table).limit(limit)).mappings().all()
+    return {"table": name, "rows": [dict(r) for r in rows]}

cfg/sample/link/docker-compose.yml

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+# Link — Fixture DB bridge
+name: ${DEPLOYMENT_NAME}_link
+
+services:
+  link:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: ${DEPLOYMENT_NAME}_link
+    environment:
+      DB_HOST: db
+      DB_PORT: 5432
+      DB_NAME: ${POSTGRES_DB}
+      DB_USER: ${POSTGRES_USER}
+      DB_PASSWORD: ${POSTGRES_PASSWORD}
+    ports:
+      - "${LINK_PORT:-8121}:8000"
+    networks:
+      - default
+
+networks:
+  default:
+    external: true
+    name: ${NETWORK_NAME}

cfg/sample/link/main.py

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+"""Link — DB bridge for the fixture invoicing app.
+
+Exposes a small HTTP API that wraps SQLAlchemy access to the fixture's
+postgres so soleprint tools can read/write without touching the app.
+"""
+
+from fastapi import FastAPI
+
+from adapters.sqlalchemy_bridge import router as db_router
+
+app = FastAPI(title="Link — Fixture Bridge")
+
+
+@app.get("/health")
+def health():
+    return {"status": "ok", "target": "fixture-invoicing"}
+
+
+app.include_router(db_router, prefix="/db")

cfg/sample/link/requirements.txt

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+fastapi==0.115.0
+uvicorn[standard]==0.32.0
+sqlalchemy==2.0.36
+psycopg2-binary==2.9.10