Add enterprise appliance experience Phase 1 foundation

tests/fixtures/README.md

@@ -0,0 +1,18 @@
+# Appliance Test Fixtures
+
+## Supported Baseline
+
+Capture the exact prior released revision, package/ISO checksum, Ubuntu version, product category,
+commercial tier, schema version and enabled components before migration testing. A moving `main`
+checkout is not a valid baseline.
+
+## Restore Fixture Requirements
+
+- Synthetic users, audit events, settings and operational state only.
+- No real credentials, signed licenses, customer documents or private logs.
+- Valid checksums and a documented schema/product version.
+- Representative Workstation and Server install records.
+- Valid, missing/staging, expired, invalid-signature and mismatch license fixtures using test keys.
+- Corrupt, incomplete and incompatible backup fixtures for negative testing.
+
+Fixtures containing secrets or customer content MUST NOT enter source control.