feat(bootstrap): vault init/unseal + capture to encrypted config (T05)

foundation-vault (hashicorp/vault:1.18, digest-pinned) with integrated raft
storage in foundation-vault-data (-> /vault/file, which the entrypoint chowns to
the vault user), IPC_LOCK for mlock, internal only (8200 unpublished). Init +
unseal reuse the olsitec-core pattern but over docker-exec/SSH (ADR-007): the
foundation-vault-init command inits 1-of-1 Shamir, unseals, and emits keys + root
token on stdout — marked secret and NOT streamed (logging:Stderr) so they never
reach the terminal/logs (D2). run.sh captures them into vaultCredentials:* (the
one bootstrap secret that cannot live in Vault, CONTRACT_002 §2.4) with an
idempotent guard that avoids churning the config. vault-unseal.sh is the
passphrase-gated reboot helper (ADR-004): reads keys from config, unseals over an
SSH stdin pipe. run.sh also now pins the Pulumi backend per-process
(PULUMI_BACKEND_URL) instead of a global `pulumi login`.

Live on cx33 Helsinki: initialized + unsealed (raft 1.18.5), keys captured to
encrypted config, idempotent re-up reuses stored keys, container-restart reseal
recovered by vault-unseal.sh. Acceptance T05 met.

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

bootstrap/Pulumi.foundation.yaml

@@ -59,4 +59,8 @@ config:
     secure: v1:svEvJ5K9u+FMnpV/:RztjS8VMSxrdgpBtbNpBPA6gfPLVgnABp77diBC6nWGHZRnG
   foundation:backup.offsiteSecretKey:
     secure: v1:lkkGBjgmJqVziusc:gpmw5lkfFAjXzeFikhtQnvWObYpKD3Bq5XSmrBA/vlLaoqqxFGAAO4Cq7V8nOLZ926x3fXukPQI=
+  vaultCredentials:unsealKeys:
+    secure: v1:9YpTkFoQanMwxAQV:dJ4YmXS0aOTHPbuK1H6AJ0SAJ0CjYX0iIyLOQAUNfsOWLsSy5TXxPpGecieBWkzc4AALDkJNlQN9Xo6Q0ZcaSg==
+  vaultCredentials:rootToken:
+    secure: v1:OUpYMjnaftxMUKjv:2m+dydQopXGRleeX6ddhYSHgHP7HHZXYLAvQHXUvaA91qajoxU+VugDB/Rs=
 encryptionsalt: v1:5YhUt8BVfH0=:v1:DPCHl+7zwn4RaMPj:A19tZzBlZ1NmDtTWrHreEKk5e8idyw==