Fix PocketID config lookup when multiple admins exist

_get_pocketid_config / _get_allowed_group selected an admin row with an
unordered LIMIT 1. With more than one admin (e.g. the seeded password admin
plus a passkey-linked admin), this non-deterministically returned an admin
without PocketID config — making the passkey button disappear (available=false)
and group gating inconsistent. Add _config_admin() which prefers the admin that
actually has an issuer set, then falls back to the lowest-id admin.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/api/auth.py

@@ -14,10 +14,32 @@ from app.models.user import User
 router = APIRouter()
 
 
+async def _config_admin(db: AsyncSession):
+    """The admin row that holds instance-wide PocketID settings.
+
+    Settings live on an admin user row, but there can be more than one admin.
+    Prefer the admin that actually has an issuer configured; otherwise fall back
+    to the lowest-id admin. Without this, an unordered LIMIT 1 could return an
+    admin with no config and make PocketID look disabled / gating inconsistent.
+    """
+    result = await db.execute(
+        select(User)
+        .where(User.is_admin == True, User.pocketid_issuer.isnot(None))
+        .order_by(User.id)
+        .limit(1)
+    )
+    admin = result.scalar_one_or_none()
+    if admin is None:
+        result = await db.execute(
+            select(User).where(User.is_admin == True).order_by(User.id).limit(1)
+        )
+        admin = result.scalar_one_or_none()
+    return admin
+
+
 async def _get_pocketid_config(db: AsyncSession):
     """Get PocketID config from DB (admin user) falling back to env vars."""
-    result = await db.execute(select(User).where(User.is_admin == True).limit(1))
-    admin = result.scalar_one_or_none()
+    admin = await _config_admin(db)
     issuer = (admin and admin.pocketid_issuer) or settings.pocketid_issuer
     client_id = (admin and admin.pocketid_client_id) or settings.pocketid_client_id
     client_secret = (admin and admin.pocketid_client_secret) or settings.pocketid_client_secret
@@ -26,8 +48,7 @@ async def _get_pocketid_config(db: AsyncSession):
 
 async def _get_allowed_group(db: AsyncSession):
     """Group a PocketID user must belong to in order to sign in (None = allow all)."""
-    result = await db.execute(select(User).where(User.is_admin == True).limit(1))
-    admin = result.scalar_one_or_none()
+    admin = await _config_admin(db)
     group = (admin and admin.pocketid_allowed_group) or settings.pocketid_allowed_group
     return (group or "").strip() or None