Map admins: owners invite friends to co-manage maps

Owners can invite players by name from the map workshop; invitees accept
from their dashboard and then manage the map (details, locations,
submission, refresh, contributions, appeals) through owner-delegated
checks. Adds the map_admins table, invite/admin API endpoints, dashboard
invite box, workshop admin management, and Russian translations.

supabase/migrations/20261031120000_map_admins.sql

@@ -0,0 +1,23 @@
+-- Map owners can invite other accounts to manage their maps together. Invites
+-- stay pending until the invitee accepts from their dashboard; accepted admins
+-- act through the owner, so map RPC checks keep working unchanged.
+create table public.map_admins (
+  id uuid primary key default gen_random_uuid(),
+  dataset_id uuid not null references public.datasets(id) on delete cascade,
+  user_id uuid not null references auth.users(id) on delete cascade,
+  invited_by uuid not null references auth.users(id) on delete cascade,
+  state text not null default 'pending' check(state in ('pending','accepted')),
+  created_at timestamptz not null default now(),
+  responded_at timestamptz,
+  constraint map_admins_unique unique(dataset_id,user_id),
+  constraint map_admins_no_self check(user_id<>invited_by),
+  constraint map_admins_response check(
+    (state='pending' and responded_at is null) or
+    (state='accepted' and responded_at is not null)
+  )
+);
+create index map_admins_user_state on public.map_admins(user_id,state);
+create index map_admins_dataset on public.map_admins(dataset_id);
+
+-- Service role only: invites and membership are managed through the API.
+alter table public.map_admins enable row level security;