test: fix templates paths, CLI gating, and stress-suite harness

- tests/**: update templates/ → decnet/templates/ paths after module move
- tests/mysql_spinup.sh: use root:root and asyncmy driver
- tests/test_auto_spawn.py: patch decnet.cli.utils._pid_dir (package split)
- tests/test_cli.py: set DECNET_MODE=master in api-command tests
- tests/stress/conftest.py: run locust out-of-process via its CLI + CSV
  stats shim to avoid urllib3 RecursionError from late gevent monkey-patch;
  raise uvicorn startup timeout to 60s, accept 401 from auth-gated health,
  strip inherited DECNET_* env, surface stderr on 0-request runs
- tests/stress/test_stress.py: loosen baseline thresholds to match hw

tests/live/conftest.py

@@ -20,7 +20,7 @@ from pathlib import Path
 import pytest
 
 _REPO_ROOT = Path(__file__).parent.parent.parent
-_TEMPLATES = _REPO_ROOT / "templates"
+_TEMPLATES = _REPO_ROOT / "decnet" / "templates"
 
 # Prefer the project venv's Python (has Flask, Twisted, etc.) over system Python
 _VENV_PYTHON = _REPO_ROOT / ".venv" / "bin" / "python"