feat: add spreadsheet async imports

supabase/migrations/202606290014_spreadsheet_import_async_metadata.sql

@@ -0,0 +1,28 @@
+alter table public.content_import_jobs
+  add column if not exists execution_mode text not null default 'sync',
+  add column if not exists queued_at timestamptz,
+  add column if not exists locked_at timestamptz,
+  add column if not exists locked_by text,
+  add column if not exists attempt_count integer not null default 0,
+  add column if not exists max_attempts integer not null default 3,
+  add column if not exists next_attempt_at timestamptz,
+  add column if not exists parser_metadata jsonb not null default '{}'::jsonb;
+
+do $$
+begin
+  if not exists (select 1 from pg_constraint where conname = 'content_import_jobs_execution_mode_check') then
+    alter table public.content_import_jobs
+      add constraint content_import_jobs_execution_mode_check
+      check (execution_mode in ('sync', 'async'));
+  end if;
+
+  if not exists (select 1 from pg_constraint where conname = 'content_import_jobs_attempts_check') then
+    alter table public.content_import_jobs
+      add constraint content_import_jobs_attempts_check
+      check (attempt_count >= 0 and max_attempts > 0 and attempt_count <= max_attempts);
+  end if;
+end $$;
+
+create index if not exists idx_content_import_jobs_async_queue
+  on public.content_import_jobs(tenant_id, status, next_attempt_at, created_at)
+  where execution_mode = 'async' and status = 'pending';