Rename Go client package from mciasgoclient to mcias

- Update package declaration in client.go
- Update error message strings to reference new package name
- Update test package and imports to use new name
- Update README.md documentation and examples with new package name
- All tests pass

web/templates/pgcreds.html

@@ -12,6 +12,7 @@
   {{range .Creds}}
   <div style="border:1px solid var(--color-border);border-radius:6px;padding:1rem;margin-bottom:1rem">
     <dl style="display:grid;grid-template-columns:140px 1fr;gap:.35rem .75rem;font-size:.9rem;margin-bottom:.75rem">
+      <dt class="text-muted">Credential ID</dt><dd><code style="font-size:.8rem;color:var(--color-fg-muted)">{{.ID}}</code></dd>
       <dt class="text-muted">Service Account</dt><dd>{{.ServiceUsername}}</dd>
       <dt class="text-muted">Host</dt><dd>{{.PGHost}}:{{.PGPort}}</dd>
       <dt class="text-muted">Database</dt><dd>{{.PGDatabase}}</dd>