M6: send-code rate-limited only per IP, so a victim's number could be
SMS-flooded from rotating IPs. Add a per-mobile bucket (same 5/hour policy)
keyed by the validated mobile.
M7: /oauth/token/refresh reused the presented refresh token verbatim (no
rotation) and never re-checked the user. The rotation infra already existed
(issueTokens mints a fresh refresh token) — the controller just discarded it.
Now revoke the presented token (single-use), issue a fresh pair, and reject a
suspended user (status != 1).
Regressions: tests/Auth/SendCodeMobileRateLimitTest,
tests/Auth/RefreshTokenRotationTest (both fail without the fix).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
