docs(readme): refresh all READMEs for the current 12-package suite (#100)

- Root README: add repo-auth + lightbridge to the belt table with dedicated
  sections; add npm badges + workspace-layout rows for repo-auth, lightbridge,
  auth-core, core-otel; correct the "eight -> twelve packages" counts (3 spots);
  add the lightbridge docs entry.
- Fix the pre-rename GitHub repo URL (vymalo/opencode-oauth2 ->
  ADORSYS-GIS/lightbridge-opencode-toolbeit) in the root, browser, browser-mcp
  and extension READMEs. npm @vymalo/* package links are left intact.
- Add the missing @vymalo/opencode-repo-auth README (the published package had
  none, so its npm page was blank).
- lightbridge README: projectId is now fully optional (omit -> default project).

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>