Address second round of PR review feedback

- Replace getConfig<T> with getMetadata/setMetadata on CliAuth, removing
  the unsafe type parameter in favor of returning unknown
- Move updateInstanceConfig from cli-module-auth public API to
  CliAuth.setMetadata, removing the cross-package dependency
- Rename 'config' to 'metadata' in StoredInstance and storage schemas
- Add zod validation at consumer sites (cli-module-actions) for
  type-safe metadata access
- Fix zod imports to use zod/v3 for compatibility with zod v4
- Add proper-lockfile to cli-node for metadata write locking
- Refactor cli-node storage from fs-extra to node:fs
- Remove @backstage/cli-module-auth dependency from cli-module-actions

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

packages/cli-node/package.json

@@ -42,6 +42,7 @@
     "commander": "^12.0.0",
     "fs-extra": "^11.2.0",
     "pirates": "^4.0.6",
+    "proper-lockfile": "^4.1.2",
     "semver": "^7.5.3",
     "yaml": "^2.0.0",
     "zod": "^3.25.76 || ^4.0.0"
@@ -50,6 +51,7 @@
     "@backstage/backend-test-utils": "workspace:^",
     "@backstage/cli": "workspace:^",
     "@backstage/test-utils": "workspace:^",
+    "@types/proper-lockfile": "^4",
     "@types/yarnpkg__lockfile": "^1.1.4"
   },
   "optionalDependencies": {