v0.54.0: Phase 2b — restore-from-recovery-unit + fail-closed data-key gate

Restore recreates an app from its on-drive unit + the guest's own secrets,
regenerating nothing. reconcileRestoreSecrets (pure, unit-tested) merges the unit's
non-secret env with secrets recovered from the live app.yaml and FAILS CLOSED if a
data-encrypting key is unrecoverable (refuse — a PBS whole-guest restore is needed —
rather than regenerate and corrupt). Resettable secrets missing → warn + proceed.

- backup: RestoreFromRecoveryUnit (manifest -> recover secrets -> gate -> restore
  volumes -> recreate definition + redeploy w/ re-pull); falls back to volume-only.
- seams: RecoverStackSecrets/RecreateStackFromUnit (adapter +encKey),
  stacks.RedeployFromEnv. Wired into /backup/restore.
- tests: gate (refuse/proceed/verbatim) + data_key parsing.

Gate + reconcile + data_key parsing unit-tested; capture live-validated (v0.53.1).
Full readable-data e2e vs AdventureLog needs the auth-gated dashboard restore — pending.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

controller/internal/stacks/metadata_test.go

@@ -0,0 +1,40 @@
+package stacks
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// TestDataKeyParsing proves the catalog `data_key: true` annotation flows through .felhom.yml parsing
+// into Metadata.DataKeyEnvVars() — the capture-side half of the Phase 2b fail-closed mechanism. The
+// fail-closed gate itself is unit-tested in internal/backup (reconcileRestoreSecrets).
+func TestDataKeyParsing(t *testing.T) {
+	dir := t.TempDir()
+	// Mirrors adventurelog/.felhom.yml: SECRET_KEY is a data-encrypting key, DB_PASSWORD is resettable.
+	yml := `display_name: AdventureLog
+deploy_fields:
+  - env_var: SECRET_KEY
+    label: "Titkosítási kulcs"
+    type: secret
+    data_key: true
+  - env_var: DB_PASSWORD
+    label: "Adatbázis jelszó"
+    type: secret
+`
+	if err := os.WriteFile(filepath.Join(dir, ".felhom.yml"), []byte(yml), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	meta := LoadMetadata(dir)
+	dk := meta.DataKeyEnvVars()
+	if len(dk) != 1 || dk[0] != "SECRET_KEY" {
+		t.Fatalf("DataKeyEnvVars() = %v, want [SECRET_KEY]", dk)
+	}
+
+	// Both secrets are sensitive (stripped from the unit); only SECRET_KEY is a data_key (fail-closed).
+	sens := SensitiveEnvVars(&meta)
+	if len(sens) != 2 {
+		t.Errorf("SensitiveEnvVars() = %v, want both SECRET_KEY and DB_PASSWORD", sens)
+	}
+}