fix(vault): prevent CPU-burning init loop with marker file + idempotent checks

Root cause: init scripts ran repeatedly (on container restart) and tried
vault secrets enable / vault auth enable for already-existing paths.
Vault logged ERRORs and burned 40-84% CPU in the loop.

Fix:
- Marker file /vault/data/.init-complete skips re-initialization
- vault secrets list / vault auth list checks before enable calls
- No more "path already in use" errors on subsequent runs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vault/init-secrets.sh

@@ -24,8 +24,12 @@ done
 
 echo "Vault is ready. Initializing secrets..."
 
-# Enable KV v2 secrets engine at 'secret/' (usually enabled in dev mode)
-vault secrets enable -version=2 -path=secret kv 2>/dev/null || echo "KV engine already enabled"
+# Enable KV v2 secrets engine at 'secret/' (only if not already enabled)
+if ! vault secrets list -format=json 2>/dev/null | grep -q '"secret/"'; then
+  vault secrets enable -version=2 -path=secret kv
+else
+  echo "KV engine already enabled — skipping"
+fi
 
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