Add enterprise appliance experience Phase 1 foundation

specs/001-enterprise-experience/migrations.md

@@ -0,0 +1,26 @@
+# SQLite Migration and Rollback Procedure
+
+## Rules
+
+1. Read the current schema version before application startup writes new data.
+2. Create a verified pre-migration backup of the database and required companion state.
+3. Apply sequential idempotent migrations in one exclusive transaction where SQLite permits.
+4. Record the new version only after all statements and validation checks succeed.
+5. On failure, roll back the transaction, preserve the original database and record a redacted error.
+6. Never downgrade destructively. Restore the pre-migration backup when rollback requires an older
+   application version.
+
+## Validation
+
+- Fresh database reaches the latest version.
+- Each supported previous version upgrades exactly once.
+- Re-running the migration is a no-op.
+- Interrupted/failed migration leaves a usable prior database or verified recovery copy.
+- Existing users, sessions, audit history, licensing state, settings and supported customer data
+  remain readable.
+- Backup compatibility is checked before any restore mutation.
+
+## Rollback Evidence
+
+Record source and target schema versions, backup path/checksum, start/end time, result, correlation ID,
+validation outcome, and recovery action without storing secrets or customer content.