Benchmark: kultainen esimerkki + zensical-dokumentointiohjeet

- golden-examples/todo/: 6/6 PASS referenssitoteutus
  - SQLAlchemy 2.0 (DeclarativeBase, Mapped, mapped_column)
  - Pydantic v2 (ConfigDict)
  - PEP 621 pyproject.toml, Python >=3.14
  - Uniikki testidata per testi
- CODE_SYSTEM päivitetty: few-shot kultaisesta esimerkistä
- DOCUMENTATION.md: zensical-dokumentointiohjeet

network-poc/tests/golden-examples/todo/pyproject.toml

@@ -0,0 +1,11 @@
+[project]
+name = "todo-app"
+version = "0.1.0"
+requires-python = ">=3.14"
+dependencies = [
+    "fastapi",
+    "uvicorn[standard]",
+    "sqlalchemy",
+    "pytest",
+    "httpx",
+]