feat: poblar scaffold inicial del shape rest-api/python

Reemplaza el placeholder mínimo previo por el scaffold canónico del
golden path rest-api/python (entry point para tier free-trial):

- code/app/main.py — FastAPI con /health (sin DB), /metrics, middleware
  correlation_id, settings Pydantic
- code/tests/ — pytest + httpx TestClient (sin testcontainers, sin Docker)
- helm/APP_NAME/ — chart minimal: Deployment, Service, IngressRoute,
  NetworkPolicy. SIN Job Alembic, SIN ServiceMonitor, SIN claim de BD
- coralware-shape.yaml — shapeVersion 1.0.0, minTier free-trial,
  promotionPath -> web-backend-python cuando se requiera persistencia
- .gitea/workflows/APP_NAME-build.yaml — invoca reusable workflow ADR-038
  + job helm-deploy con KUBECONFIG_TENANT_B64

Diferencias con web-backend/python: sin alembic, sin BD, sin
testcontainers, NetworkPolicy sin acceso a ns-addons.

Placeholders __APP_NAME__, __TIER__, __TENANT_ID__, __TENANT_ID_NODASHES__
serán sustituidos server-side por repo-provisioner.

El openspec/ del golden path NO se sincroniza al repo Gitea (gobernanza
interna de Coralware).

Refs: ADR-027 (Golden Paths), ADR-038 (CI), ADR-053 (referencia anatomía).

code/Dockerfile

@@ -0,0 +1,26 @@
+# Multi-stage para imagen final lean.
+# Stage 1: deps — instala dependencias Python en una venv aislada.
+# Stage 2: runtime — copia código y venv, corre como user no-root con FS read-only.
+
+FROM python:3.12-slim AS deps
+WORKDIR /build
+COPY requirements.txt .
+RUN python -m venv /venv \
+ && /venv/bin/pip install --no-cache-dir --upgrade pip \
+ && /venv/bin/pip install --no-cache-dir -r requirements.txt
+
+FROM python:3.12-slim AS runtime
+WORKDIR /app
+
+COPY --from=deps /venv /venv
+ENV PATH="/venv/bin:$PATH"
+
+COPY app /app/app
+
+RUN useradd -u 1001 -r appuser \
+ && chown -R appuser:appuser /app
+USER appuser
+
+EXPOSE 8000
+
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--no-access-log"]