feat(vault): add keytar dependency for OS keychain access

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: plosson

bun.lock

@@ -60,6 +60,7 @@
     "commander": "^14.0.2",
     "google-auth-library": "^10.0.0",
     "gray-matter": "^4.0.3",
+    "keytar": "^7.9.0",
     "libsodium-wrappers": "^0.8.1",
     "long": "^5.3.2",
     "plist": "^3.1.0",