fix(rbac): port Better-Auth user auto-provision into legacy ./src tree (GRO-2052)
Ports the Better-Auth user-table auto-provision branch from canonical apps/api into the deployed ./src/middleware/rbac.ts so the owner-bypass in pets.ts is reachable for Better-Auth email/password customers. OIDC account branch retained as backward-compat fallback. Adds 5 rbac.test.ts cases and UAT_PLAYBOOK pre-condition docs.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Flea Flicker <flea@groombook.dev>
Co-committed-by: Flea Flicker <flea@groombook.dev>