fix(auth): show installation-aware registration guidance

[SHAURYAKSHARMA24]

Summary

Add a public read-only registration-mode endpoint exposing only open versus approval configuration. Show development openness and approval-mode setup accurately, without describing a first user as an administrator or exposing bootstrap/account counts.

Linked issue

Related to #510.

Scope

Audit F19; baseline dev df0e82be3d7b2b7d846eefc1bcf82bde834936f2. This corrects independently verified existing behavior and advances the linked issue without adding product scope.

What changed

Add a public read-only registration-mode endpoint exposing only open versus approval configuration. Show development openness and approval-mode setup accurately, without describing a first user as an administrator or exposing bootstrap/account counts.

Acceptance criteria completed

Implementation and targeted regression coverage below. See remaining work for conditions not verified.

Testing performed

41 auth and OpenAPI tests passed; 4 registration-page tests passed; frontend lint and production build passed; Ruff and generated API contract drift check passed.

Current head: 0c5bd39f1ac987c4e94acb3d328dab1297525eed; check snapshot appears below.

Screenshots

Local screenshots and browser measurements are recorded in the remediation delivery report where applicable. Backend-only changes use contract/regression evidence.

Security and data considerations

Preserves owner scoping, source provenance, sealed graph contracts and historical data. No security gate weakened. Rollback: revert this scoped commit; see issue for migration/deployment implications.

Dependencies and blocked work

Independent dev-based PR unless explicitly stated in the issue. No unmerged changes included.

Scope changes or remaining work

Additive API/schema; DTO regenerated. Reconcile generated DTO with upload PR #526 when integrating. Browser visual review and current-head CI required.

Please review @parthrohit22.

Contributor checklist

• Targets dev; dedicated fork branch from latest dev; issue claimed.

• Scope/evidence recorded; unrelated changes and secrets excluded.

• Targeted validation results reported accurately.

• Required current-head CI and maintainer review complete.

Current-head remediation validation

Head: 0c5bd39f1ac987c4e94acb3d328dab1297525eed.

41 auth and OpenAPI tests passed; 4 registration-page tests passed; frontend lint and production build passed; Ruff and generated API contract drift check passed.

Additive API/schema; DTO regenerated. Reconcile generated DTO with upload PR #526 when integrating. Browser visual review and current-head CI required.

Checks at delivery: Repository Hygiene: SUCCESS; Analyze (javascript-typescript): SUCCESS; Analyze (python): SUCCESS; API Contract Drift: SUCCESS; Frontend: FAILURE; Backend: SUCCESS; Docker Build: SUCCESS; Marketing Site: SUCCESS; Prototype Browser Acceptance: SKIPPED; Vercel: FAILURE; CodeQL: SUCCESS. Required checks/reviews must pass before merge; deployment authorization was not granted.

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