feat(admin): delete a whitelist entry, and stop hiding a broken mail setup

Three operator gaps, all found the same way — a person could not sign up and the
app showed nobody anything.

- DELETE /api/admin/invites/{id} with a delete control on both the pending
  requests and the previously-decided list. Deny keeps the row so the person
  cannot immediately re-ask; delete forgets the address. Refused with 409 while
  a User row exists for it, because is_allowed reads that row and removing it
  would revoke a live user's access with no other sign — the list ships
  has_account so the UI withholds the button instead of offering one that fails.
- Email is fail-soft by design, which had come to mean invisible. _send() now
  records an email_undelivered notification for every admin when a message is
  skipped or rejected, naming the message that was lost, throttled to one an
  hour. /api/me carries email_configured, driving a standing warning on
  Configuration → Email / SMTP and above the access-request list.
- The sign-in card's Create account / Forgot password / Didn't get the email
  views are history entries (useHistorySubview), so Back returns to the previous
  view instead of only moving the address bar.

Also: the per-test rate-limiter reset sweeps every loaded app.* module rather
than a hand-kept list of three — this change added a limiter outside it.

backend/app/routes/admin.py

@@ -1,6 +1,7 @@
 """Admin-only onboarding: review access requests (Invites), approve/deny, manual add.
 Also the demo-account admin surface: the demo email whitelist + a manual state reset."""
 
+from collections.abc import Iterable
 from datetime import datetime, timezone
 
 from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException
@@ -31,7 +32,18 @@ from app.utils import iso, valid_email
 router = APIRouter(prefix="/api/admin", tags=["admin"])
 
 
-def _serialize(inv: Invite) -> dict:
+def _accounts_for(db: Session, emails: Iterable[str]) -> set[str]:
+    """Which of these addresses already have an account. Batched, so listing the invites costs one
+    extra query. An invite whose address has an account must not be deletable: `is_allowed` reads
+    this row, so removing it would silently revoke a live user's access."""
+    wanted = {e.lower() for e in emails if e}
+    if not wanted:
+        return set()
+    rows = db.execute(select(User.email).where(User.email.in_(wanted))).scalars()
+    return {e.lower() for e in rows if e}
+
+
+def _serialize(inv: Invite, *, has_account: bool = False) -> dict:
     return {
         "id": inv.id,
         "email": inv.email,
@@ -40,6 +52,8 @@ def _serialize(inv: Invite) -> dict:
         "requested_at": iso(inv.requested_at),
         "decided_at": iso(inv.decided_at),
         "decided_by": inv.decided_by,
+        # Drives the delete affordance: an entry backed by an account is not removable here.
+        "has_account": has_account,
     }
 
 
@@ -56,7 +70,8 @@ def list_invites(
     rows = db.execute(stmt.order_by(Invite.requested_at.desc())).scalars().all()
     order = {"pending": 0, "approved": 1, "denied": 2}
     rows.sort(key=lambda i: order.get(i.status, 9))
-    return [_serialize(i) for i in rows]
+    accounts = _accounts_for(db, (i.email for i in rows))
+    return [_serialize(i, has_account=(i.email or "").lower() in accounts) for i in rows]
 
 
 def _activate_user_by_email(db: Session, email: str) -> None:
@@ -107,7 +122,7 @@ def approve_invite(
     inv = _decide(db, invite_id, admin, approved=True)
     _activate_user_by_email(db, inv.email)
     background.add_task(email_mod.send_access_approved, inv.email)
-    return _serialize(inv)
+    return _serialize(inv, has_account=bool(_accounts_for(db, [inv.email])))
 
 
 @router.post("/invites/{invite_id}/deny")
@@ -121,7 +136,7 @@ def deny_invite(
     # account is activated, so this is an email only (the requester has no in-app inbox yet).
     inv = _decide(db, invite_id, admin, approved=False)
     background.add_task(email_mod.send_access_denied, inv.email)
-    return _serialize(inv)
+    return _serialize(inv, has_account=bool(_accounts_for(db, [inv.email])))
 
 
 class AddInviteIn(BaseModel):
@@ -150,7 +165,41 @@ def add_invite(
     )
     db.commit()
     _activate_user_by_email(db, email)
-    return _serialize(inv)
+    return _serialize(inv, has_account=bool(_accounts_for(db, [email])))
+
+
+@router.delete("/invites/{invite_id}")
+def delete_invite(
+    invite_id: int,
+    admin: User = Depends(admin_user),
+    db: Session = Depends(get_db),
+) -> dict:
+    """Remove a whitelist/request entry outright — the counterpart to add_invite, for an address that
+    never became an account (an approval added by mistake, or one that is no longer wanted). Denying
+    a request keeps the row so the person cannot immediately re-ask; deleting it forgets them, and a
+    fresh request from that address starts over as pending.
+
+    Refused once an account exists: `is_allowed` reads this row, so removing it would silently revoke
+    a live user's access. Delete the USER instead — purge_user removes the invite along with it."""
+    inv = db.get(Invite, invite_id)
+    if inv is None:
+        raise HTTPException(status_code=404, detail="No such invite")
+    if _accounts_for(db, [inv.email]):
+        raise HTTPException(
+            status_code=409,
+            detail="That address already has an account — delete the account instead.",
+        )
+    audit.record(
+        db,
+        admin.id,
+        AuditAction.INVITE_DELETE,
+        target_type="invite",
+        target_id=inv.id,
+        summary=inv.email,
+    )
+    db.delete(inv)
+    db.commit()
+    return {"deleted": invite_id}
 
 
 # --- Users & roles --------------------------------------------------------------------

backend/app/routes/me.py

@@ -13,6 +13,7 @@ from app.auth import (
     optional_current_user,
     purge_user,
 )
+from app import email as email_mod
 from app import sysconfig
 from app.db import get_db
 from app.models import Invite, User
@@ -98,11 +99,16 @@ def get_me(
     if user is None:
         return {"authenticated": False}
     pending_invites = 0
+    # Admin-only, because it drives an operator warning: email is fail-soft, so a half-filled SMTP
+    # config costs verification links, password resets and access-request notices with nothing
+    # visible anywhere. Surfacing it here puts the warning on the screens where onboarding happens.
+    email_configured = True
     if user.role == "admin":
         pending_invites = (
             db.scalar(select(func.count()).select_from(Invite).where(Invite.status == "pending"))
             or 0
         )
+        email_configured = email_mod.email_enabled()
     return {
         "authenticated": True,
         "id": user.id,
@@ -121,6 +127,7 @@ def get_me(
         "can_read": has_read_scope(user),
         "can_write": has_write_scope(user),
         "pending_invites": pending_invites,
+        "email_configured": email_configured,
         "preferences": user.preferences or {},
     }