fix(auth): register page creates the credential row, so new accounts can log in

[mmcintosh]

Description

The register page posts to POST /auth/register/form (htmx), not to the JSON /auth/register. The form handler inserted auth_user but never the auth_account credential row that Better Auth signs in with.

As a result:

• registration returned 200, and the first user was even made admin;
• every sign-in then failed with "Invalid email or password" (Better Auth logs Credential account not found), until a later full bootstrap happened to backfill the row (with the KV marker, up to 24 hours).

The JSON route already wrote both rows. Only the path the UI uses was broken.

The deployment docs made it worse. They say the ADMIN_EMAIL / ADMIN_PASSWORD secrets create the admin at bootstrap, and nothing in the code reads them.

Refs #1054 (reported in detail by elpastiche on that issue).

Changes

• routes/auth.ts, POST /auth/register/form:
  • writes auth_user and the credential row in one db.batch, exactly as the JSON route does;
  • for the first user, seeds document types and RBAC before creating the account, the same idempotent calls /auth/seed-admin makes;
  • checks that the admin role actually landed. If the role assignment fails, it removes the rows it just created and reports the failure, so a retry works instead of hitting "email already exists";
  • optional custom profile fields are saved after that step. A failure there is logged, and the account is still created.
• Docs: the deployment, configuration, troubleshooting and core-plugin pages, plus docs/deployment.md.
  • They now say the first account registered becomes the admin, with a note to do it right after deploying.
  • They no longer document ADMIN_EMAIL / ADMIN_PASSWORD.
  • The "create admin via API" example is gone: the JSON route always creates a viewer.

Testing

• auth-register-form.integration.test.ts (new, 6 tests): real SQLite, then sign-in through a real Better Auth instance.

  • The first (admin) user and a later user both sign in.
  • A wrong password gets 401.
  • A duplicate email writes no second user or credential row.
  • The first user on a database with no RBAC seed ends up an RBAC admin.
  • A forced role-assignment failure leaves no rows, and the retry succeeds.

  On main's handler, 5 of the 6 fail; the wrong-password case is the control and passes either way. The tests also pass on Better Auth 1.7.7 (fix(auth): move to Better Auth 1.7.7 and better-auth-cloudflare 0.4.1 #1103).

Unit Tests

• Added/updated unit tests
• All unit tests passing (this branch: 1936 / 0; all five batch PRs merged: 2000 / 0)

E2E Tests

• Added/updated E2E tests: 113-register-form-login.spec.ts (@auth). It registers through the real page, then logs in through POST /auth/login, and a wrong password gets 401. It waits out spec 37 switching registration off on the shared preview database instead of toggling the setting itself.
• All E2E tests passing (not run locally, per the repo's E2E policy)

Screenshots/Videos

N/A. The register page looks the same; the change is what the server writes. The docs changes are text only.

Checklist

• Code follows project conventions
• Tests added/updated and passing
• Type checking passes
• No console errors or warnings
• Documentation updated (if needed)