Baseline: docker stack, provisioning tools, test-data, gateway-as-files (pre-PrimeBAT build)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

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+# Gateway API token (mint with: python3 tools/provision.py mint-token)
+.env
+# MariaDB password read by the 'local' file secret provider (written by provision.py)
+ignition/gateway/config/secrets/
+# Fresh-reset rollback copy
+ignition/gateway.bak/
+# Gateway-maintained content-addressed caches + probe output (never author/commit)
+ignition/gateway/**/.resources/
+ignition/gateway/projects/.probe/
+__pycache__/
+.pytest_cache/