fix: defer secure credential loading until ready

Load encrypted account credentials only after Electron reaches its ready state so Windows DPAPI is available during startup. Retry transient secure-storage discovery instead of caching an unavailable result for the process lifetime. Add hidden two-process DPAPI regression coverage for the real renderer IPC path and bump the public version to 2.1.40.

lib/secret-store.js

@@ -30,7 +30,6 @@ function getSafeStorage() {
       return _safeStorageCache;
     }
   } catch {}
-  _safeStorageCache = null;
   return null;
 }