fix(auth): reopen a pre-dated approval instead of auto-granting it

Replaces the activation added in ea931dc, which round 2 of the review showed was
a real weakening: on a no-SMTP instance it made a standing whitelist entry a
bearer grant — the first anonymous party to register an approved-but-unclaimed
address got an immediately usable account under that identity, with no
attestation, no admin action and no signal anywhere. The verify-time activation
had the same shape one step removed, and neither site ran the SEC-10 preset-
password guard or left an audit trail.

Keep a human in the loop instead. An approval granted before any account existed
was a decision about the ADDRESS, so registration reopens the invite
(upsert_pending_invite gains revive_approved, used only by the register worker).
The request lands in the Access-requests queue, approving it runs
_activate_user_by_email — and with it revoke_preset_password_if_unverified — and
the account activates. One mechanism, already audited, no new grant path, and
the "awaiting admin approval" copy is honest again.

The explicit commit from the previous commit still matters: with an invite
already pending, upsert returns without committing and _issue_token is gated on
SMTP, so a no-SMTP registration was still being rolled back.

Also from round 2: gate the admin notice on a fresh decision (matching the two
other upsert callers) so a retry no longer re-pings every admin, and reset the
module-level rate limiters between tests — the suite pooled every login into one
300s window and was two logins short of failing an unrelated test with a 429.

backend/app/routes/auth.py

@@ -147,16 +147,25 @@ def _client_ip(request: Request) -> str:
     return peer
 
 
-def upsert_pending_invite(db: Session, email: str) -> Invite | None:
+def upsert_pending_invite(
+    db: Session, email: str, *, revive_approved: bool = False
+) -> Invite | None:
     """Idempotently record an access request. Returns the Invite if a *new* pending row
-    was created (so the caller can notify admins), else None for already-known emails."""
+    was created (so the caller can notify admins), else None for already-known emails.
+
+    `revive_approved` is for the registration path only. An approval granted BEFORE any account
+    existed was a decision about the ADDRESS, not about whoever has now set a password on it, so the
+    request goes back in front of a human rather than becoming an automatic grant. It also un-strands
+    the registrant: an approved invite never appears in the Access-requests queue and `_decide` 409s
+    on an already-decided one, so nothing in the admin UI could otherwise activate the account."""
     email = (email or "").lower()
     if not valid_email(email):
         return None
     inv = db.execute(select(Invite).where(Invite.email == email)).scalar_one_or_none()
     if inv is not None:
-        # Let a previously-denied person ask again; don't disturb approved/pending rows.
-        if inv.status == "denied":
+        # Let a previously-denied person ask again; don't disturb a pending row (the admin already
+        # has that request in front of them).
+        if inv.status == "denied" or (revive_approved and inv.status == "approved"):
             inv.status = "pending"
             inv.requested_at = datetime.now(timezone.utc)
             inv.decided_at = None
@@ -636,29 +645,25 @@ def _register_account(email: str, password: str) -> None:
             # no-op as the pre-check hit — roll back and stop.
             db.rollback()
             return
-        upsert_pending_invite(db, email)  # admin-approval gate (commits only when it writes a row)
-        # Honour an approval the admin had ALREADY given for this address. Without this the account
-        # lands is_active=False against a non-pending invite: it never shows up in the Access-requests
-        # queue (which lists pending only) and approve_invite 409s on an already-decided invite, so
-        # the admin has no obvious way to let the person in. Attestation still gates it — with SMTP on
-        # the address is unverified at this point, so activation waits for the verify link (see
-        # verify_email_confirm). With no SMTP there is no attestation to wait for and the admin's
-        # whitelist is by design the only gate, the very one add_invite already activates on.
-        if not email_ok and is_allowed(db, email):
-            user.is_active = True
-        # Persist the account ourselves. upsert_pending_invite commits only when it actually inserts
-        # (or revives) an invite row, and _issue_token below only runs with SMTP on — so for an email
-        # the admin had ALREADY approved, on an instance with no SMTP, nothing along this path
-        # committed and the flushed user was silently rolled back when the session closed. The
-        # would-be user got a uniform "ok" and no account. Commit unconditionally; it is a no-op
-        # when upsert already committed the same transaction.
+        # admin-approval gate. revive_approved: an approval that predates the account is re-opened so
+        # a human binds it to THIS registration — that keeps the SEC-10 preset-password guard in the
+        # loop (approve_invite runs it) and puts the request somewhere the admin can actually see.
+        inv = upsert_pending_invite(db, email, revive_approved=True)
+        # Persist the account ourselves. upsert_pending_invite commits only when it actually writes an
+        # invite row, and _issue_token below only runs with SMTP on — so when a request for this
+        # address was already pending, on an instance with no SMTP, nothing along this path committed
+        # and the flushed user was silently rolled back when the session closed. The would-be user got
+        # a uniform "ok" and no account. Commit unconditionally; it is a no-op when upsert already
+        # committed the same transaction.
         db.commit()
         if email_ok:
             raw = _issue_token(db, user, "verify", VERIFY_TTL)
             # Fragment (#), not a query token: keeps the token out of proxy/access logs + Referer (SB3).
             email_mod.send_verify_email(email, f"{_app_base()}/#verify={raw}")
         admins = admin_notify_emails(db)
-        if admins:
+        # Only when there is a fresh decision to make, matching the other two call sites. Without the
+        # guard an address whose request was already pending re-pinged every admin on each retry.
+        if inv is not None and admins:
             email_mod.send_admin_new_request(admins, email)
 
 
@@ -672,12 +677,6 @@ def verify_email_confirm(body: TokenIn, db: Session = Depends(get_db)) -> dict:
             status_code=400, detail="This verification link is invalid or has expired."
         )
     user.email_verified = True
-    # Ownership is attested now (only the mailbox owner can follow this link), so an approval the
-    # admin granted BEFORE the person signed up can finally be honoured. Otherwise they sit at
-    # is_active=False behind a request no admin screen shows — the invite is already decided, so it
-    # is absent from the pending queue and approve_invite would 409 on it.
-    if not user.is_active and is_allowed(db, user.email):
-        user.is_active = True
     db.commit()
     return {"ok": True}